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.

判断树是否相等

根全为空

或者全部为空，则值相等，子孙相等

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