经典面试题——二叉树

来源：互联网发布：get it hot 编辑：程序博客网时间：2024/05/22 11:06
#include <cstdio>#include <iostream>#include <queue>using namespace std;struct Node {    Node *l, *r;    int x;    Node(int x=0, Node *l=NULL, Node *r=NULL):x(x),l(l),r(r) {}    };class Tree {    public:        Tree(Node* root) {            this->root = root;        }                Node* getRoot() {            return root;        }                Node* buildTree() {            int x;            cin >> x;            if(x != -1) {                Node* curRoot = new Node(x);                curRoot->l = buildTree();                curRoot->r = buildTree();                return curRoot;            } else {                return NULL;            }        }                void print_pre_order(Node* cur) {            if(cur == NULL)    return;            printf("%d ", cur->x);            print_pre_order(cur->l);            print_pre_order(cur->r);        }                void print_in_order(Node* cur) {            if(cur == NULL)    return;            print_in_order(cur->l);            printf("%d ", cur->x);            print_in_order(cur->r);        }                void print_post_order(Node* cur) {            if(cur == NULL)    return;            print_post_order(cur->l);            print_post_order(cur->r);            printf("%d ", cur->x);        }                void print_level_order(Node* cur) {            if(cur==NULL)    return;            queue<Node*> que;            que.push(cur);            while(!que.empty()) {                Node* c = que.front();                que.pop();                printf("%d ", c->x);                if(c->l)    que.push(c->l);                if(c->r)    que.push(c->r);            }        }                int getNodeNum(Node* root) {            if(root==NULL)    return 0;            return getNodeNum(root->l) + getNodeNum(root->r) + 1;        }                int getLeafNum(Node* root) {            if(root==NULL)    return 0;            if(root->l==NULL && root->r==NULL)    return 1; // 是叶子节点             return getLeafNum(root->l) + getLeafNum(root->r); // 非叶子节点         }                int getHeight(Node* root) {            if(root==NULL)    return 0;            return max(getHeight(root->l), getHeight(root->r))+1; // 每个节点都加1，所以统计了所有节点数         }                void turn_all_node(Node *root) {            if(root==NULL)    return;            if(root->l==NULL && root->r==NULL)    return; // 两个分支均为空，交换无意义             // 左右分支交换             Node* temp = root->l;            root->l = root->r;            root->r = temp;            if(root->l)    turn_all_node(root->l);            if(root->r)    turn_all_node(root->r);        }                bool isExist(Node *root, int x) {            if(root == NULL)    return 0;            if(root->x == x)    return 1;            return isExist(root->l, x) || isExist(root->r, x);        }        // 求二叉树第K层的节点个数        int getKnum(Node *root, int k) {            if(root==NULL || k < 1)    return 0;            if(k==1)    return 1;            return getKnum(root->l, k-1)+getKnum(root->r, k-1);        }        // 判断两棵二叉树是否结构相同        bool cmp(Node *a, Node *b) {            if(a == NULL && b == NULL) return 1;             if(a==NULL || b==NULL)    return 0;            return cmp(a->l, b->l) && cmp(a->r, b->r);        }    private:        Node *root;};int main (){    // 1 2 4 -1 -1 5 -1 6 -1 -1 3 7 -1 8 -1 -1 -1    // 6 4 2 3 -1 -1 -1 -1 5 1 -1 -1 7 -1 -1    Node* root;    Tree tree(root);    root = tree.buildTree();        // 前、中、后序遍历     tree.print_pre_order(root);    printf("\n");        tree.print_in_order(root);    printf("\n");        tree.print_post_order(root);    printf("\n");        tree.print_level_order(root);    printf("\n");        //节点个数    cout << "Node num: " << tree.getNodeNum(root) << endl;         // 叶子个数     cout << "Leaf num: " << tree.getLeafNum(root) << endl;        // 树高     cout << "Height: " << tree.getHeight(root) << endl;        // 二叉树镜像     tree.turn_all_node(root);    tree.print_level_order(root);    printf("\n");        //子树的节点查找 //    int x;//    while(cin >> x) {//        printf("%s\n", tree.isExist(root, x) ? "Yes!":"No.");//    }    //求二叉树第K层的节点个数//    int k;//    while(cin >> k) {//        printf("The %dth floor nodes num: %d\n", k, tree.getKnum(root, k));//    }    return 0;}
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