LeetCode-100. Same Tree

100. Same Tree

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

树的题目大都用的递归思想，这道题更是如此，先从根节点开始判断，之后再递归比较左子树、右子树即可。

class Solution {
public:
    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;
    	else if(p->val!=q->val)
			return false;
		return isSameTree(p->left,q->left)&&isSameTree(p->right,q->right);		
	}
};