[leetcode]: 100. Same Tree

1.题目

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.

判断两棵二叉树是否相等。相等的定义是：结构相同，节点的元素值相同

2.分析

可以用递归来实现。
对于每个根结点
1）节点元素值是否相同
2）左子树是否相同
3）右子树是否相同

3.代码

bool isSameTree(TreeNode* p, TreeNode* q) {    if (p == NULL && q == NULL)        return true;    else if ((p == NULL && q != NULL) || (p != NULL &&q == NULL))        return false;    return p->val == q->val && isSameTree(p->left, q->left) && isSameTree(p->right, q->right);}