Problem:

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.

 

Analysis:

recursion

 

A possible answer:

/** * 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->val != q->val || p==NULL || q==NULL)            return false;        else            return isSameTree(p->left,q->left) && isSameTree(p->right,q->right);    }};