LeetCode OJ Convert Sorted List to Binary Search Tree

Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST.

之前在Sicily做过，就是实现一个AVL树了。

struct TreeNodeNew {    int val;    TreeNodeNew *left;    TreeNodeNew *right;int bf;TreeNodeNew(int val = 0, TreeNodeNew * left = NULL, TreeNodeNew * right = NULL, int bf = 0) {this->val = val;this->left = left;this->right = right;this->bf = bf;}};class Solution {public:TreeNode * sortedListToBST(ListNode * head) {TreeNodeNew * ansNew = NULL;ListNode * temp = head;while (temp) {avlInsert(ansNew, temp->val);temp = temp->next;}TreeNode * ans = NULL;if (ansNew) reBuild(ansNew, ans);return ans;}void reBuild(TreeNodeNew * &nowNew, TreeNode * &now) {now = new TreeNode(nowNew->val);if (nowNew->left) reBuild(nowNew->left, now->left);if (nowNew->right) reBuild(nowNew->right, now->right);}inline int MAX(int a, int b) {if (a > b) return a + 1;return b + 1;}void avlInsert(TreeNodeNew * &root, const int entry) {bool unbalanced;avlInsertInside(root, entry, unbalanced);}void lR(TreeNodeNew * &parent) {TreeNodeNew * child = parent->left;if (child->bf == 1) {parent->left = child->right;child->right = parent;parent->bf = 0;parent = child;}else {TreeNodeNew * grandChild = child->right;parent->left = grandChild->right;child->right = grandChild->left;grandChild->right = parent;grandChild->left = child;switch (grandChild->bf) {case 0:parent->bf = child->bf = 0;break;case 1:parent->bf = -1;child->bf = 0;break;case -1:parent->bf = 0;child->bf = 1;}parent = grandChild;}parent->bf = 0;}void rR(TreeNodeNew * &parent) {TreeNodeNew * child = parent->right;if (child->bf == -1) {parent->right = child->left;child->left = parent;parent->bf = 0;parent = child;}else {TreeNodeNew * grandChild = child->left;parent->right = grandChild->left;child->left = grandChild->right;grandChild->right = child;grandChild->left = parent;switch (grandChild->bf) {case 0:parent->bf = child->bf = 0;break;case -1:parent->bf = 1;child->bf = 0;break;case 1:parent->bf = 0;child->bf = -1;}parent = grandChild;}parent->bf = 0;}void avlInsertInside(TreeNodeNew * &parent, const int x, bool & unbalanced) {if (parent == NULL) {parent = new TreeNodeNew(x, 0, 0, 0);unbalanced = true;}else if (x < parent->val) {avlInsertInside(parent->left, x, unbalanced);if (unbalanced) {switch (parent->bf) {case 0:parent->bf = 1;break;case -1:parent->bf = 0;unbalanced = false;break;case 1:lR(parent);unbalanced = false;}}}else if (x > parent->val) {avlInsertInside(parent->right, x, unbalanced);if (unbalanced) {switch (parent->bf) {case 0:parent->bf = -1;break;case 1:parent->bf = 0;unbalanced = false;break;case -1:rR(parent);unbalanced = false;}}}else {unbalanced = false;}}};