算法作业_38(2017.6.20第十八周)

226. Invert Binary Tree

Invert a binary tree.

     4   /   \  2     7 / \   / \1   3 6   9

to

     4   /   \  7     2 / \   / \9   6 3   1

100. Same Tree

Given two binary trees, write a function to check if they are equal or not.

Two binary trees are considered equal if they are structurally identical and the nodes have the same value.

解析：二叉树的反转和判断问题，简单的递归问题：

Invert Binary Tree：

/** * Definition for a binary tree node. * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:    TreeNode* invertTree(TreeNode* root) {        if(root == NULL) return NULL;        invertTree(root->left);        invertTree(root->right);        swap(root->left,root->right);        return root ;    }};

Same Tree：

/** * Definition for a binary tree node. * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */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) || (p->val!=q->val))            return false;        return isSameTree(p->left,q->left) && isSameTree(p->right,q->right);    }};