LeetCode 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.

分析：

题目要求判断两棵树是否相同，首先判断根节点是否相同，如果根节点相同，分别判断左、右子树是否相同。

代码如下：

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