Leetcode_Same Tree

地址：http://oj.leetcode.com/problems/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.

思路：用递归的思路。如果p和q都为空，返回true。若p和q都非空，

1. 比较p->val 和 q->val

2. 然后，递归调用 p->left 和 q->left

3. 最后，递归调用 p->right 和 q->right

只有走完三步才返回true，否则返回false

参考代码：

updated SECOND TRIAL, 4ms

/**
 * Definition for binary tree
 * 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)
            return !q;
        else if(!q)
            return false;
        return p->val == q->val && isSameTree(p->left, q->left) && isSameTree(p->right, q->right);
    }
};