leecode每日一题02-same tree [easy]

题目描述：

Given two binary trees, write a function to check if they are the same or not.

Two binary trees are considered the same if they are structurally identical and the nodes have the same value.

Example 1:

Input:     1         1
          / \       / \
         2   3     2   3

        [1,2,3],   [1,2,3]

Output: true
Example 2:

Input:     1         1
          /           \
         2             2

        [1,2],     [1,null,2]

Output: false
Example 3:

Input:     1         1
          / \       / \
         2   1     1   2

        [1,2,1],   [1,1,2]

Output: false

 

求解方法：

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

 小结：最喜欢二叉树之类的解法，找到诀窍后，采用递归方法，很有四两拨千斤的快感。