100、Same Tree

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.

解题思路：

python版本：

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def isSameTree(self, p, q):
        """
        :type p: TreeNode
        :type q: TreeNode
        :rtype: bool
        """
        if p==None and q==None:
            return True
        elif p==None:
            return q==None
        elif q==None:
            return p==None
        elif p.val!=q.val:
            return False
        
        return self.isSameTree(p.left, q.left) and self.isSameTree(p.right, q.right)
        

c++版本：

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