【leetcode】面试leetcode代码
来源：互联网 发布：csol for mac 编辑：程序博客网 时间：2024/06/10 20:18
- 字符串
1. leetcode Valid Palindrome
class Solution {public: bool isPalindrome(string s) { if (s.size() <= 0) return true; string::iterator left = s.begin(); string::iterator right = s.end(); while (left < right) { if (!isalnum(*left)) left++; else if (!isalnum(*right)) right--; else { if (tolower(*left++) != tolower(*right--)) return false; } } return true; }};2. leetcode String to Integer (atoi)
class Solution {public: int atoi(const char *str) { if (str == NULL) return -1; long long res = 0; int sign = 1; const char *pStr = str; while (*pStr != '\0' && isspace(*pStr)) { pStr++; } if (*pStr == '+') pStr++; else if (*pStr == '-') { sign = -1; pStr++; } while (*pStr != '\0') { if (*pStr<'0' || *pStr>'9') break; res = res * 10 + *pStr - '0'; if (res > INT_MAX) { if (sign == -1) return INT_MIN; else return INT_MAX; } pStr++; } return sign * res; }};3. leetcode Implement strStr()
class Solution {public: char *strStr(char *haystack, char *needle) { if (haystack == NULL) return NULL; if (needle==NULL) return haystack; char *pSrc = haystack; char *pSub = needle; while (*pSrc!='\0' && *pSub!='\0') { if (*pSrc++ != *pSub++) { pSub = needle; pSrc = ++haystack; } } if (*pSub == '\0') return haystack; return NULL; }};- 1. leetcode Valid Palindrome
- 1. leetcode Valid Palindrome
- 1. leetcode Valid Palindrome
- 1. leetcode Valid Palindrome
- 1. leetcode Valid Palindrome
- 1. leetcode Valid Palindrome
- 1. leetcode Valid Palindrome
- 1. leetcode Valid Palindrome
- 链表
1. leetcode Reverse Nodes in k-Group
class Solution {public: ListNode *reverseKGroup(ListNode *head, int k) { if (head==NULL || head->next==NULL || k<=1) return head; ListNode preHead(-1); preHead.next = head; ListNode *pre = &preHead; ListNode *pTemp; while (head != NULL) { ListNode *pEnd = head; for (int i=1; i<k && head!=NULL; i++) { head = head->next; } if (head == NULL) return preHead.next; pTemp = pEnd->next; for (int i=1; i<k; i++) { ListNode *pNext = pTemp->next; pTemp->next = pre->next; pre->next = pTemp; pTemp = pNext; } pre = pEnd; pEnd->next = pTemp; head = pTemp; } return preHead.next; }};2. leetcode Swap Nodes in Pairs
class Solution {public: ListNode *swapPairs(ListNode *head) { return swapN(head, 2); } ListNode *swapN(ListNode *head, int n) { if (head==NULL || head->next==NULL || n<=1) return head; ListNode preHead(-1); preHead.next = head; ListNode *pre = &preHead; ListNode *pFront = head;ListNode *pTemp; while (pFront != NULL) { ListNode *pEnd = pFront; int tempN = n; while (pFront && --tempN>0) { pFront = pFront->next; } if (pFront == NULL) return preHead.next;pTemp = pEnd; for (int i=1; i<n; i++) {pTemp = pTemp->next; head = pTemp->next; pTemp->next = pre->next; pre->next = pTemp; pTemp = head; } pre = pEnd; pFront = head; pEnd->next = head; } return preHead.next; }};3. leetcode Remove Nth Node From End of List
class Solution {public: ListNode *removeNthFromEnd(ListNode *head, int n) { if (head==NULL || n<=0) return head; ListNode preHead(-1); preHead.next = head; ListNode *pTemp = &preHead; head = &preHead; while (n-->0 && pTemp!=NULL) { pTemp = pTemp->next; } while (pTemp->next != NULL) { head = head->next; pTemp = pTemp->next; } head->next = head->next->next; return preHead.next; }};4. leetcode Remove Duplicates from Sorted List II
class Solution {public: ListNode *deleteDuplicates(ListNode *head) { if (head==NULL || head->next==NULL) return head; ListNode preHead(-1); preHead.next = head; ListNode *rear = &preHead; ListNode *cur = head; ListNode *pNext=cur->next; int flag = 0; while (pNext != NULL) { if (cur->val == pNext->val) { flag = 1; pNext = pNext->next; } else { if (flag == 1) { rear->next = pNext; flag = 0; } else { rear = cur; } cur = pNext; pNext = pNext->next; } } if (flag == 1) rear->next = pNext; return preHead.next; }};5. leetcode Remove Duplicates from Sorted List
class Solution {public: ListNode *deleteDuplicates(ListNode *head) { if (head==NULL || head->next==NULL) return head; ListNode *pCur, *pNext; for (pCur=head, pNext=pCur->next; pNext!=NULL; ) { if (pCur->val == pNext->val) { pCur->next = pNext->next; } else { pCur = pNext; } pNext = pNext->next; } return head; }};6. leetcode Partition List
class Solution {public: ListNode *partition(ListNode *head, int x) { if (head==NULL || head->next==NULL) return head; ListNode left(-1); ListNode right(-1); ListNode *pLeft = &left; ListNode *pRight = &right; while (head != NULL) { if (head->val < x) { pLeft->next = head; pLeft = pLeft->next; } else { pRight->next = head; pRight = pRight->next; } head = head->next; } pRight->next = head; pLeft->next = right.next; return left.next; }};7. leetcode Reverse Linked List II
class Solution {public: ListNode *reverseBetween(ListNode *head, int m, int n) { if (head==NULL || m<=0 || n<=0 || m>=n) return head; ListNode preHead(-1); preHead.next = head; ListNode *pBeg = &preHead; ListNode *pEnd; ListNode *pTemp; for (int i=1; i<=m; i++) { pTemp = pBeg; pBeg = pBeg->next; } pEnd = pBeg->next; for (int i=m+1; i<=n; i++) { head = pEnd->next; pEnd->next = pTemp->next; pTemp->next = pEnd; pEnd = head; } pBeg->next = head; return preHead.next; }};8. leetcode Linked List Cycle
class Solution {public: bool hasCycle(ListNode *head) { if (head==NULL || head->next==NULL) return false; ListNode *pFast = head; ListNode *pSlow = head; while (pFast!=NULL && pFast->next!=NULL) { pFast = pFast->next->next; pSlow = pSlow->next; if (pFast == pSlow) return true; } return false; }};9. leetcode Merge Two Sorted Lists
class Solution {public: ListNode *mergeTwoLists(ListNode *l1, ListNode *l2) { if (l1 == NULL) return l2; if (l2 == NULL) return l1; ListNode preHead(-1); ListNode *pNew = &preHead; while (l1 && l2) { if (l1->val < l2->val) { pNew->next = l1; l1 = l1->next; } else { pNew->next = l2; l2 = l2->next; } pNew = pNew->next; } if (l1) pNew->next = l1; if (l2) pNew->next = l2; return preHead.next; }};10. leetcode Sort List
class Solution {public: ListNode *sortList(ListNode *head) { if (head==NULL || head->next==NULL) return head; ListNode *pFast = head; ListNode *pSlow = head; ListNode *second; while (pFast && pFast->next) { second = pSlow; pFast = pFast->next->next; pSlow = pSlow->next; } second->next = NULL; ListNode *l1 = sortList(head); ListNode *l2 = sortList(pSlow); head = mergeList(l1, l2); return head; } ListNode *mergeList(ListNode *l1, ListNode *l2) { if (l1 == NULL) return l2; if (l2 == NULL) return l1; ListNode preHead(-1); ListNode *p = &preHead; while (l1 && l2) { if (l1->val < l2->val) { p->next = l1; l1 = l1->next; } else { p->next = l2; l2 = l2->next; } p = p->next; } if (l1) p->next = l1; if (l2) p->next = l2; return preHead.next; }};11. leetcode Rotate List
class Solution {public: ListNode *rotateRight(ListNode *head, int k) { if (head==NULL || head->next==NULL || k<=0) return head; ListNode *pPre = head; ListNode *pTemp; int len = 0; while (pPre != NULL) { len++; pTemp = pPre; pPre = pPre->next; } k = len - k%len; pTemp->next = head; for (int i=0; i<k; i++) { pTemp = pTemp->next; head = head->next; } pTemp->next = NULL; return head; }};12. leetcode Insertion Sort List
class Solution {public: ListNode *insertionSortList(ListNode *head) { if (head==NULL || head->next==NULL) return head; ListNode preHead(-1); preHead.next = head; ListNode *pPre = head->next; head->next = NULL; while (pPre != NULL) { ListNode *first = preHead.next; ListNode *pNext = pPre->next; head = &preHead; while (first != NULL) { if (first->val >= pPre->val) break; else { head = first; first = first->next; } } pPre->next = head->next; head->next = pPre; pPre = pPre->next; pPre = pNext; } return preHead.next; }};13. leetcode Reorder List
class Solution {public: void reorderList(ListNode *head) { if (head==NULL || head->next==NULL || head->next->next==NULL) return; ListNode *pFast = head; ListNode *pSlow = head; ListNode *pTemp; while (pFast!=NULL && pFast->next!=NULL) { pTemp = pSlow; pSlow = pSlow->next; pFast = pFast->next->next; }pTemp->next = NULL;pSlow = reverseList(pSlow); head = mergeList(head, pSlow); } ListNode *reverseList(ListNode *head) { if (head==NULL || head->next==NULL) return head; ListNode *pCur = head->next; ListNode *pNext; head->next = NULL; while (pCur != NULL) { pNext = pCur->next; pCur->next = head; head = pCur; pCur = pNext; }return head; } ListNode *mergeList(ListNode *l1, ListNode *l2) { if (l1 == NULL) return l2; if (l2 == NULL) return l1; ListNode preHead(-1); ListNode *pTemp = &preHead; while (l1 && l2) { pTemp->next = l1; l1 = l1->next; pTemp = pTemp->next; pTemp->next = l2; pTemp = pTemp->next; l2 = l2->next; } if (l1 != NULL) pTemp->next = l1;if (l2 != NULL) pTemp->next = l2;return preHead.next; }};14. leetcode LRU Cache
class LRUCache{private: struct CacheNode { int key; int value; struct CacheNode *prev; struct CacheNode *next; CacheNode(int k, int v) :key(k), value(v) {} }; public: LRUCache(int capacity) { this->capacity = capacity; } int get(int key) { if (cacheMap.find(key) == cacheMap.end()) return -1; cacheList.splice(cacheList.begin(), cacheList, cacheMap[key]); cacheMap[key] = cacheList.begin(); return cacheMap[key]->value; } void set(int key, int value) { if (cacheMap.find(key) == cacheMap.end()) { if (cacheList.size() == capacity) { cacheMap.erase(cacheList.back().key); cacheList.pop_back(); } cacheList.push_front(CacheNode(key, value)); cacheMap[key] = cacheList.begin(); } else { cacheMap[key]->value = value; cacheList.splice(cacheList.begin(), cacheList, cacheMap[key]); cacheMap[key] = cacheList.begin(); } }private: list<CacheNode> cacheList; unordered_map<int, list<CacheNode>::iterator> cacheMap; int capacity;};15. leetcode Linked List Cycle II
class Solution {public: ListNode *detectCycle(ListNode *head) { if (head == NULL) return NULL; ListNode *pFast = head; ListNode *pSlow = head; ListNode *pHead = head; while (pFast && pFast->next) { pFast = pFast->next->next; pSlow = pSlow->next; if (pFast == pSlow) { while (pHead != pSlow) { pHead = pHead->next; pSlow = pSlow->next; } return pHead; } } return NULL; }};1. leetcode Valid Palindrome
1. leetcode Valid Palindrome
- 树
1. leetcode Maximum Depth of Binary Tree
class Solution {public: int maxDepth(TreeNode *root) { if (root == NULL) return 0; if (root->left==NULL && root->right==NULL) return 1; return max(maxDepth(root->left), maxDepth(root->right)) + 1; }};2. leetcode Same Tree
class Solution {public: bool isSameTree(TreeNode *p, TreeNode *q) { if (p==NULL && q==NULL) return true; if ((p==NULL && q!=NULL) || (p!=NULL && q==NULL)) return false; if (p->val == q->val) { return isSameTree(p->left, q->left) && isSameTree(p->right, q->right); } else return false; }};3. leetcode Balanced Binary Tree
class Solution {public: bool isBalanced(TreeNode *root) { if (root == NULL) return true; int left = heightTree(root->left) + 1; int right = heightTree(root->right) + 1; return (abs(left-right)<=1) && isBalanced(root->left) && isBalanced(root->right); } int heightTree(TreeNode *root) { if (root == NULL) return 0; if (root->left==NULL && root->right==NULL) return 1; return max(heightTree(root->left), heightTree(root->right)) + 1; }};4. leetcode Binary Tree Preorder Traversal
class Solution {public: vector<int> preorderTraversal(TreeNode *root) { vector<int> res; stack<TreeNode *> sTemp; if (root == NULL) return res; sTemp.push(root); while (!sTemp.empty()) { TreeNode *temp = sTemp.top(); res.push_back(temp->val); sTemp.pop(); if (temp->right) sTemp.push(temp->right); if (temp->left) sTemp.push(temp->left); } return res; }};5. leetcode Binary Tree Inorder Traversal
class Solution {public: vector<int> inorderTraversal(TreeNode *root) { vector<int> res; stack<TreeNode *> sTemp; TreeNode *pRoot = root; while (pRoot!=NULL || !sTemp.empty()) { while (pRoot) { sTemp.push(pRoot); pRoot = pRoot->left; } if (!sTemp.empty()) { TreeNode *temp = sTemp.top(); res.push_back(temp->val); sTemp.pop(); if (temp->right) { pRoot = temp->right; } } } return res; }};6. leetcode Binary Tree Postorder Traversal
class Solution {public: vector<int> postorderTraversal(TreeNode *root) { vector<int> res; stack<TreeNode *> sTemp; TreeNode *pCur = root; TreeNode *pPre = NULL; while (pCur!=NULL || !sTemp.empty()) { while (pCur != NULL) { sTemp.push(pCur); pCur = pCur->left; } pCur = sTemp.top(); if (pCur->right==NULL || pCur->right==pPre) { res.push_back(pCur->val); pPre = pCur; sTemp.pop(); pCur = NULL; } else pCur = pCur->right; } return res; }};7. leetcode Binary Tree Level Order Traversal
class Solution {public: vector<vector<int> > levelOrder(TreeNode *root) { vector<vector<int> > res; vector<int> vec; if (root == NULL) return res; queue<TreeNode *> curQueue, nextQueue; curQueue.push(root); while (!curQueue.empty()) { while (!curQueue.empty()) { TreeNode *temp = curQueue.front(); vec.push_back(temp->val); curQueue.pop(); if (temp->left) nextQueue.push(temp->left); if (temp->right) nextQueue.push(temp->right); } swap(curQueue, nextQueue); res.push_back(vec); vec.clear(); } return res; }};8. leetcode Binary Tree Zigzag Level Order Traversal
class Solution {public: vector<vector<int> > zigzagLevelOrder(TreeNode *root) { vector<vector<int> > res; if (root == NULL) return res; queue<TreeNode *> cur, nex; cur.push(root); bool isReverse = false; while (!cur.empty()) { vector<int> vec; while (!cur.empty()) { TreeNode *temp = cur.front(); vec.push_back(temp->val); cur.pop(); if (temp->left) nex.push(temp->left); if (temp->right) nex.push(temp->right); } if (isReverse == false) { isReverse = true; } else { isReverse = false; reverse(vec.begin(), vec.end()); } res.push_back(vec); swap(cur, nex); } return res; }};9. leetcode Validate Binary Search Tree
class Solution {public: bool isValidBST(TreeNode *root) { return isValid(root, INT_MIN, INT_MAX); } bool isValid(TreeNode *root, int le, int ri) { if (root == NULL) return true; if (!(root->val>le && root->val<ri)) return false; return isValid(root->left, le, root->val) && isValid(root->right, root->val, ri); }};10. leetcode Binary Tree Level Order Traversal II
class Solution {public: vector<vector<int> > levelOrderBottom(TreeNode *root) { vector<vector<int> > res; if (root == NULL) return res; queue<TreeNode *> cur, nex; cur.push(root); while (!cur.empty()) { vector<int> vec; while (!cur.empty()) { TreeNode *temp = cur.front(); cur.pop(); vec.push_back(temp->val); if (temp->left) nex.push(temp->left); if (temp->right) nex.push(temp->right); } res.push_back(vec); swap(cur, nex); } reverse(res.begin(), res.end()); return res; }};11. leetcode Sum Root to Leaf Numbers
class Solution {public: int sumNumbers(TreeNode *root) { return dfs(root, 0); } int dfs(TreeNode *root, int sum) { if (root==NULL) return 0; if (root->left==NULL && root->right==NULL) return sum*10 + root->val; return dfs(root->left, sum*10 + root->val) + dfs(root->right, sum*10 + root->val); }};12. leetcode Recover Binary Search Tree
class Solution {public: void recoverTree(TreeNode *root) { TreeNode *s1 = NULL; TreeNode *s2 = NULL; TreeNode *pre = NULL; findTwo(root, s1, s2, pre); if (s1!=NULL && s2!=NULL) { swap(s1->val, s2->val); } } void findTwo(TreeNode *root, TreeNode *&s1, TreeNode *&s2, TreeNode *&pre) { if (root == NULL) return; findTwo(root->left, s1, s2, pre); if (pre!=NULL && pre->val > root->val) { s2 = root; if (s1 == NULL) s1 = pre; } pre = root; findTwo(root->right, s1, s2, pre); }};13. leetcode Symmetric Tree
class Solution {public: bool isSymmetric(TreeNode *root) { if (root == NULL) return true; return isLeftRight(root->left, root->right); } bool isLeftRight(TreeNode *le, TreeNode *ri) { if (le==NULL && ri==NULL) return true; if (le==NULL || ri==NULL) return false; if (le->val != ri->val) return false; return isLeftRight(le->left, ri->right) && isLeftRight(le->right, ri->left); }};14. leetcode Flatten Binary Tree to Linked List
class Solution {public: void flatten(TreeNode *root) { if (root == NULL) return; while (root) { if (root->left) { TreeNode *pre = root->left; while (pre->right) pre = pre->right; pre->right = root->right; root->right = root->left; root->left = NULL; } root = root->right; } }};15. leetcode Populating Next Right Pointers in Each Node II
class Solution {public: void connect(TreeLinkNode *root) { if (root == NULL) return; queue<TreeLinkNode *> cur, nex; cur.push(root); while (!cur.empty()) { TreeLinkNode preHead(-1); TreeLinkNode *p = &preHead; while (!cur.empty()) { TreeLinkNode *temp = cur.front(); cur.pop(); p->next = temp; p = p->next; if (temp->left) nex.push(temp->left); if (temp->right) nex.push(temp->right); } p->next = NULL; swap(cur, nex); } }};16. leetcode Populating Next Right Pointers in Each Node
class Solution {public: void connect(TreeLinkNode *root) { if (root == NULL) return; queue<TreeLinkNode *> cur, nex; cur.push(root); while (!cur.empty()) { TreeLinkNode preHead(-1); TreeLinkNode *p = &preHead; while (!cur.empty()) { TreeLinkNode *temp = cur.front(); cur.pop(); p->next = temp; p = p->next; if (temp->left) nex.push(temp->left); if (temp->right) nex.push(temp->right); } p->next = NULL; swap(cur, nex); } }};17. leetcode Construct Binary Tree from Preorder and Inorder Traversal
class Solution {public: TreeNode *buildTree(vector<int> &preorder, vector<int> &inorder) { if (preorder.empty() || inorder.empty() || preorder.size()!=inorder.size()) return NULL; return buildT(preorder, 0, preorder.size()-1, inorder, 0, inorder.size()-1); } TreeNode *buildT(vector<int> &preorder, int pBeg, int pEnd, vector<int> &inorder, int iBeg, int iEnd) { if (pBeg > pEnd || iBeg > iEnd) return NULL; TreeNode *root = new TreeNode(preorder[pBeg]); int pos = -1; for (pos=iBeg; pos<=iEnd; pos++) { if (inorder[pos] == root->val) break; } root->left = buildT(preorder, pBeg+1, pBeg+pos-iBeg, inorder, iBeg, pos-1); root->right = buildT(preorder, pBeg+pos-iBeg+1, pEnd, inorder, pos+1, iEnd); return root; }};18. leetcode Construct Binary Tree from Inorder and Postorder Traversal
class Solution {public: TreeNode *createTree(vector<int> &inorder, int inBeg, int inEnd, vector<int> &postorder, int postBeg, int postEnd) { if (inBeg > inEnd) return NULL; int root = postorder[postEnd]; TreeNode *node = new TreeNode(root); int index; for(int i = inBeg; i <= inEnd; i++) if (inorder[i] == root) { index = i; break; } int len = index - inBeg; node->left = createTree(inorder, inBeg, index - 1, postorder, postBeg, postBeg + len - 1); node->right = createTree(inorder, index + 1, inEnd, postorder, postBeg + len, postEnd - 1); return node; } TreeNode *buildTree(vector<int> &inorder, vector<int> &postorder) { if (inorder.size() == 0) return NULL; return createTree(inorder, 0, inorder.size() - 1, postorder, 0, postorder.size() - 1); }};19. leetcode Minimum Depth of Binary Tree
class Solution {public: int minDepth(TreeNode *root) { if (root == NULL) return 0; if (root->left==NULL && root->right==NULL) return 1; if (root->left==NULL && root->right!=NULL) return minDepth(root->right) + 1; if (root->right==NULL && root->left!=NULL) return minDepth(root->left) + 1; return min(minDepth(root->left), minDepth(root->right)) + 1; } };20. leetcode Path Sum
class Solution {public: bool hasPathSum(TreeNode *root, int sum) { bool res = false; pathSum(root, sum, 0, res); return res; } void pathSum(TreeNode *root, int sum, int res, bool &fal_tru) { if (root == NULL) return; if (root->left==NULL && root->right==NULL) { if (sum == res + root->val) { fal_tru = true; return; } } if (root->left && fal_tru==false) pathSum(root->left, sum, res+root->val, fal_tru); if (root->right && fal_tru==false) pathSum(root->right, sum, res+root->val, fal_tru); } };21. leetcode Path Sum II
class Solution {public: vector<vector<int> > pathSum(TreeNode *root, int sum) { vector<vector<int> > res; vector<int> temp; pathT(root, sum, 0, res, temp); return res; } void pathT(TreeNode *root, int sum, int num, vector<vector<int> > &res, vector<int> &temp) { if (root == NULL) return; if (root->left==NULL && root->right==NULL) { if (sum == num + root->val) { temp.push_back(root->val); res.push_back(temp); temp.pop_back(); } return; } temp.push_back(root->val); pathT(root->left, sum, num+root->val, res, temp); pathT(root->right, sum, num+root->val, res, temp); temp.pop_back(); }};22. leetcode Binary Tree Maximum Path Sum
class Solution {public: int dfs(TreeNode *root) { if (root == NULL) return 0; int l = dfs(root->left); int r = dfs(root->right); int sumTemp = root->val; if (l > 0) sumTemp += l; if (r > 0) sumTemp += r; maxResult = max(maxResult, sumTemp); return max(l, r)>0 ? max(l, r) + root->val : root->val; } int maxPathSum(TreeNode *root) { if (root == NULL) return 0; maxResult = INT_MIN; dfs(root); return maxResult; }private: int maxResult;};23. leetcode Convert Sorted Array to Binary Search Tree
class Solution {public: TreeNode *sortTOBST(vector<int> &num, int beg, int end) { if (beg > end) return NULL; int mid = (beg + end)/2; TreeNode *root = new TreeNode(num[mid]); root->left = sortTOBST(num, beg, mid - 1); root->right = sortTOBST(num, mid + 1, end); return root; } TreeNode *sortedArrayToBST(vector<int> &num) { if (num.empty()) return NULL; return sortTOBST(num, 0, num.size() - 1); }};24. leetcode Convert Sorted List to Binary Search Tree
class Solution {public: TreeNode *sortedListToBST(ListNode *head) { if (head == NULL) return NULL; TreeNode *root; if (head->next == NULL) { root = new TreeNode(head->val); } else { ListNode *pFast = head; ListNode *pSlow = head; ListNode *pTemp = pSlow; while (pFast!=NULL && pFast->next!=NULL) { pFast = pFast->next->next; pTemp = pSlow; pSlow = pSlow->next; } pTemp->next = NULL; pFast = pSlow->next; root = new TreeNode(pSlow->val); root->left = sortedListToBST(head); root->right = sortedListToBST(pFast); } return root; }};25. leetcode Unique Binary Search Trees
class Solution {public: int retNum(int dp[], int beg, int end) { if (beg > end) return 1; if (dp[end-beg+1] != 0) return dp[end-beg+1]; int res = 0; for (int i=beg; i<=end; i++) { int leftNum = retNum(dp, beg, i - 1); int rightNum = retNum(dp, i + 1, end); res += leftNum * rightNum; } return (dp[end-beg+1] = res); } int numTrees(int n) { if (n <=0) return 0; int dp[n + 1]; memset(dp, 0, sizeof(dp)); return retNum(dp, 1, n); }};26. leetcode Unique Binary Search Trees II
class Solution {public: vector<TreeNode *> genTrees(int beg, int end) { vector<TreeNode *> res; if (beg > end) { res.push_back(NULL); return res; } for (int i=beg; i<=end; i++) { vector<TreeNode *> lVec = genTrees(beg, i - 1); vector<TreeNode *> rVec = genTrees(i + 1, end); for (int j=0; j<lVec.size(); j++) { for (int k=0; k<rVec.size(); k++) { TreeNode *root = new TreeNode(i); root->left = lVec[j]; root->right = rVec[k]; res.push_back(root); } } } return res; } vector<TreeNode *> generateTrees(int n) { return genTrees(1, n); }};- 数组
1. leetcode Climbing Stairs
class Solution {public: int climbStairs(int n) { if (n <= 0) return 0; int first = 0; int second = 1; int res; for (int i=1; i<=n; i++) { res = first + second; first = second; second = res; } return res; }};2. leetcode Single Number
class Solution {public: int singleNumber(int A[], int n) { if (A==NULL || n<=0) return -1; int res = A[0]; for (int i=1; i<n; i++) res ^= A[i]; return res; }};3. leetcode Merge Sorted Array
class Solution {public: void merge(int A[], int m, int B[], int n) { int i_A = m-1; int i_B = n-1; int i_total = m + n - 1; while (i_A>=0 && i_B>=0) { if (A[i_A] > B[i_B]) { A[i_total--] = A[i_A--]; } else { A[i_total--] = B[i_B--]; } } while (i_B >= 0) A[i_total--] = B[i_B--]; }};4. leetcodeRemove Element
class Solution {public: int removeElement(int A[], int n, int elem) { int pos = 0; for (int i=0; i<n; i++) { if (A[i] != elem) { A[pos++] = A[i]; } } return pos; }};5. leetcodeSpiral Matrix
class Solution {public: vector<int> spiralOrder(vector<vector<int> > &matrix) { vector<int> res; if (matrix.empty()) return res; int s_row = 0, e_row=matrix.size() - 1; int s_col = 0, e_col = matrix[0].size() - 1; while (s_row<=e_row && s_col<=e_col) { if (s_row<=e_row && s_col<=e_col) { //right for (int i=s_col; i<=e_col; i++) { res.push_back(matrix[s_row][i]); } s_row++; } if (s_row<=e_row && s_col<=e_col) { //down for (int i=s_row; i<=e_row; i++) { res.push_back(matrix[i][e_col]); } e_col--; } if (s_row<=e_row && s_col<=e_col) { //left for (int i=e_col; i>=s_col; i--) { res.push_back(matrix[e_row][i]); } e_row--; } if (s_row<=e_row && s_col<=e_col) { for (int i=e_row; i>=s_row; i--) { res.push_back(matrix[i][s_col]); } s_col++; } } return res; }};6. leetcode Spiral Matrix II
class Solution {public: vector<vector<int> > generateMatrix(int n) { vector<vector<int> >res; vector<int> temp; int m = 1; if (n <= 0) return res; int s_row = 0, e_row = n-1, s_col = 0, e_col = n-1; for (int i=0; i<n; i++) temp.push_back(0); for (int i=0; i<n; i++) res.push_back(temp); while (s_row<=e_row && s_col<=e_col) { for (int i=s_col; i<=e_col; i++) { res[s_row][i] = m++; } s_row++; for (int i=s_row; i<=e_row; i++) { res[i][e_col] = m++; } e_col--; for (int i=e_col; i>=s_col; i--) res[e_row][i] = m++; e_row--; for (int i=e_row; i>=s_row; i--) //up res[i][s_col] = m++; s_col++; } return res; }};7. leetcode Permutations
class Solution {public: bool nextPermutation(vector<int> &num) { if (num.empty()) return false; int head_item; int item; int len = num.size() - 1; for (item=num.size()-1; item>0; item--) { if (num[item-1] < num[item]) break; } if (item == 0) return false; head_item = item - 1; for (item=num.size()-1; item>head_item; item--) { if (num[head_item] < num[item]) break; } swap(num[head_item], num[item]); for (item=head_item+1; item<=len; item++, len--) { swap(num[item], num[len]); } return true; } vector<vector<int> > permute(vector<int> &num) { vector<vector<int> > ret; if (num.empty()) return ret; sort(num.begin(), num.end()); ret.push_back(num); while (nextPermutation(num)) { ret.push_back(num); } return ret; }};8. leetcode Permutations II
class Solution {public: bool nextPermutation(vector<int> &num) { if (num.empty()) return false; int head_item; int item; int len = num.size() - 1; for (item=num.size()-1; item>0; item--) { if (num[item-1] < num[item]) break; } if (item == 0) return false; head_item = item - 1; for (item=num.size()-1; item>head_item; item--) { if (num[head_item] < num[item]) break; } swap(num[head_item], num[item]); for (item=head_item+1; item<=len; item++, len--) { swap(num[item], num[len]); } return true; } vector<vector<int> > permuteUnique(vector<int> &num) { vector<vector<int> > ret; if (num.empty()) return ret; sort(num.begin(), num.end()); ret.push_back(num); while (nextPermutation(num)) ret.push_back(num); return ret; }};9. leetcode Next Permutation
class Solution {public: bool nextPermu(vector<int> &num) { if (num.empty()) return false; int head_item; int item; int len = num.size() - 1; for (item=num.size()-1; item>0; item--) { if (num[item-1] < num[item]) break; } if (item == 0) return false; head_item = item - 1; for (item=num.size()-1; item>head_item; item--) { if (num[head_item] < num[item]) break; } swap(num[head_item], num[item]); for (item=head_item+1; item<=len; item++, len--) { swap(num[item], num[len]); } return true; } void nextPermutation(vector<int> &num) { if (num.empty()) return; if (nextPermu(num) == false) { sort(num.begin(), num.end()); } }};10. leetcode Remove Duplicates from Sorted Array
class Solution {public: int removeDuplicates(int A[], int n) { if (A==NULL || n<0) return -1; if (n == 0) return 0; int start = 0; for (int i=1; i<n; i++) { if (A[start] != A[i]) A[++start] = A[i]; } return start + 1; }};11. leetcode Pascal's Triangle
class Solution {public: vector<vector<int> > generate(int numRows) { vector<vector<int> > ret; if (numRows <= 0) return ret; vector<int> temp; temp.push_back(1); ret.push_back(temp); for (int i=1; i<numRows; i++) { temp.clear(); temp.push_back(1); for (int j=1; j<i; j++) { int iTemp = ret[i-1][j-1] + ret[i-1][j]; temp.push_back(iTemp); } temp.push_back(1); ret.push_back(temp); } return ret; }}12. leetcode Pascal's Triangle II
class Solution {public: vector<int> getRow(int rowIndex) { vector<int> ret; vector<int> pre; if (rowIndex < 0) return ret; ret.push_back(1); for (int i=1; i<=rowIndex; i++) { pre = ret; ret.clear(); ret.push_back(1); for (int j=1; j<i; j++) { int iTemp = pre[j-1] + pre[j]; ret.push_back(iTemp); } ret.push_back(1); } return ret; }};1. leetcode Valid Palindrome
1. leetcode Valid Palindrome
1. leetcode Valid Palindrome
1. leetcode Valid Palindrome
- 动态规划
1. leetcode Maximum Subarray
class Solution {public: int maxSubArray(int A[], int n) { if (A==NULL || n<=0) return -1; int res = A[0]; int current = 0; for (int i=0; i<n; i++) { current += A[i]; if (res < current) res = current; if (current < 0) current = 0; } return res; }};2. leetcode Triangle
class Solution {public: int minimumTotal(vector<vector<int> > &triangle) { if (triangle.size() <= 0) return 0; for (int i=triangle.size()-2; i>=0; i--) { for (int j=0; j<=i; j++) { triangle[i][j] += min(triangle[i+1][j], triangle[i+1][j+1]); } } return triangle[0][0]; }};3. leetcode Edit Distance
class Solution {public: int minDistance(string word1, string word2) { int len1 = word1.size(); int len2 = word2.size(); int res[len1 + 1][len2 + 1]; for (int i=0; i<=len2; i++) res[0][i] = i; for (int i=0; i<=len1; i++) res[i][0] = i; for (int i=0; i<len1; i++) { for (int j=0; j<len2; j++) { if (word1[i] == word2[j]) res[i + 1][j + 1] = res[i][j]; else { res[i + 1][j + 1] = min(res[i + 1][j], res[i][j + 1]) + 1; res[i + 1][j + 1] = min(res[i + 1][j + 1], res[i][j] + 1); } } } return res[len1][len2]; }};1. leetcode Valid Palindrome
分治法
1. leetcode Sqrt(x)
class Solution {public: int sqrt(int x) { if (x < 0) return -1; if (x <= 1) return x; int left = 1; int right = x / 2; int last; while (left <= right) { int mid = (left + right) / 2; if (x/mid == mid) return mid; else if (x/mid < mid) right = mid - 1; else { left = mid + 1; last = mid; } } return last; }};2. leetcodePow(x, n)
class Solution {public: double pow(double x, int n) { if (n < 0) return 1.0 / powNext(x, -n); return powNext(x, n); } double powNext(double x, int n) { if (n == 0) return 1.0; double res = powNext(x, n/2); if (n%2 == 1) return res * res * x; else return res * res; }};- 贪心法
1. leetcode Best Time to Buy and Sell Stock
class Solution {public: int maxProfit(vector<int> &prices) { if (prices.size() < 2) return 0; int ret = 0; int cur_min = prices[0]; for (int i=1; i<prices.size(); i++) { ret = max (ret, prices[i] - cur_min); cur_min = min(cur_min, prices[i]); } return ret; }};2. leetcode Best Time to Buy and Sell Stock II
class Solution {public: int maxProfit(vector<int> &prices) { if (prices.size() < 2) return 0; int profit = 0; for (int i=1; i<prices.size(); i++) { int temp = prices[i] - prices[i - 1]; if (temp > 0) profit += temp; } return profit; }};- 细节实现
1. leetcode Reverse Integer
class Solution {public: int reverse(int x) { int sign = 1; int res = 0; if (x < 0) { sign = -1; x = -x; } while (x) { res = res * 10 + x%10; x /= 10; } return res * sign; }};1. leetcode Valid Palindrome
1. leetcode Valid Palindrome
1. leetcode Valid Palindrome
1. leetcode Valid Palindrome
1. leetcode Valid Palindrome
- 其他实现
1. IP字符串转换整数
int retLongIP(const char *strIP) {if (strIP==NULL || strlen(strIP)<7 || strlen(strIP)>15)return -1;int res = 0;int dot = 0;int shift = 24;const char *pBeg = strIP;const char *pEnd = strIP;while (*pEnd != '\0') {int temp = 0;while (*pEnd!='\0' && *pEnd!='.'){if (*pEnd>='0' && *pEnd<='9') {temp = temp * 10 + (*pEnd - '0');pEnd++;}elsereturn -1;}if (*pEnd == '.') {dot += 1;}if (pBeg==pEnd || (temp<0 && temp>255) || (*pBeg=='0' && pEnd-pBeg>1))return -1;res += (temp<<shift);shift -= 8;if (*pEnd != '\0')pBeg = ++pEnd;}if (dot != 3) return -1;return res;}
2. leetcode 约瑟夫问题
#include <stdio.h>#include <stdlib.h>#include <string.h>void yueSeFu(int a[], int n, int m) {if (a==NULL || n<=0) return;int count = n; int i = 0; //nint j = 0; //mwhile (count != 0) {if (a[i] != 0) {j++;if (j%m == 0) {j = 0;printf("%d\n", a[i]);a[i] = 0;count--;}}i++;if (i%n == 0)i = 0;}}int main(){int n, m, i;scanf("%d %d", &n, &m);int *pN = (int *)malloc(sizeof(int) * (n));if (pN == NULL)exit(-1);for (i=0; i<n; i++) {pN[i] = i + 1;}yueSeFu(pN, n, m);return 0;}3. leetcode KMP
求模式 a b a a b c a c的next函数的算法：因为已知next(1)=0,只要找出next(j+1)与next(j)之间的关系，就可以求出模式串所有next。
<span style="font-family: Arial, Helvetica, sans-serif; font-size: 12px;">next初始算法：：：：</span>
（1）next[j] = 0 j=1
（2）设next[j]=k, 于是有p(1)...p(k-1) = p(j-k+1)...p(j-1)
若p(k) = p(j) 必然有<span style="font-family: Arial, Helvetica, sans-serif; font-size: 12px;">p(1)...p(k-1)p(k) = p(j-k+1)...p(j-1)p(j) next[j+1] = next[j] + 1 ＝ k ＋1</span>
<span style="font-family: Arial, Helvetica, sans-serif; font-size: 12px;"> 若不等 </span>
void get_next(sstring T, int &next[]){ //求模式串T的next函数值并存入数组next。 j=1; k=next[j]=0; while (j<T[0]) { //计算next(j)从next(2)到next(T[0])，T[0]是T的长度 //但并不意味着只循环m-1次，因为在循环体中j的值可能不发生变化 if (k==0||T[j]==T[k])// 没有重叠真子串和（有重叠真子串但T[j]==T[k]）时//都应该得出next(j+1)的值 next[++j]=++k; else k=next(k);//否则，得不出next(j+1)的值，所以j不变，k退回到next(k)，重复匹配。}利用next值表进行匹配的过程：假设以i和j分别指示主串和模式串中正待比较的字符，若si=tj ,则i和j分别增1，否则，i不变，而j退回到next[j]的位置再比较，若j退回到值为0（即模式的第一个字符失配），则将模式继续向右滑动一个位置，即从主串的下一个字符si+1起和模式重新开始匹配。int index_KMP(sstring s, sstring t, int pos){ //利用模式串的next函数求t在主串s中第pos个字符之后的位置的KMP算法， //t非空，1<=pos<=strlength(s) i=pos; j=1; while(i<=s[0]&&j<=t[0]) { if (j==0||s[i]==t[j]){++i;++j;} else j=next[j];}if (j>t[0]) return i-t[0];else return 0;}//index_kmp1. leetcode Valid Palindrome
1. leetcode Valid Palindrome
八.
Search in Rotated Sorted Array II
class Solution {
public:
bool search(int A[], int n, int target) {
int pre = 0, last = n - 1;
while (pre <= last) {
const int mid = (pre + last) / 2;
if (A[mid] == target)
return true;
if (A[pre] < A[mid]) {
if (A[pre] <= target && A[mid] >= target)
last = mid;
else
pre = mid;
}
else if (A[pre] > A[mid]) {
if (target >= A[mid] && target <= A[last])
pre = mid;
else
last = mid;
}
else {
pre++;
}
}
return false;
}
};
//leetcode Queen
class Solution {
public:
vector<vector<string> > solveNQueens(int n) {
vector<vector<string> > res; vector<string> temp;
string ss(n, '.');
if (n <= 0)
return res;
for (int i=0; i<n; i++) {
temp.push_back(ss);
}
for (int i=0; i<=n; i++) {
row[i] = true;
mark[i] = 0;
}
for (int i=0; i<=2*n-1; i++)
line1[i] = line2[i] = true;
tryToQueen(0, n, res, temp);
return res;
}
void tryToQueen(int start, int n, vector<vector<string> > &res, vector<string> &temp) {
if (start == n) { //result
vector<string> tempT(temp);
for (int i=0; i<n; i++) {
int nrow = mark[i];
tempT[nrow][i] = 'Q';
}
res.push_back(tempT);
return;
}
for (int j=0; j<n; j++) {
if (row[j] && line1[start + j] && line2[start - j + n]) {
mark[start] = j;
row[j] = line1[start + j] = line2[start - j + n] = false;
tryToQueen(start+1, n, res, temp);
row[j] = line1[start + j] = line2[start - j + n] = true;
}
}
}
bool row[20]; int mark[20];
bool line1[40]; bool line2[40];
};
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