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：注意边界条件的判断，先判断两树是不是为空，都为空，则为true，否则递归判断存在的其他情况，判断左右子树的情况。

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

 python：

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

class Solution:
    # @param p, a tree node
    # @param q, a tree node
    # @return a boolean
    def isSameTree(self, p, q):
        if p==None and q==None:
            return True
        elif p!=None and q==None:
            return False
        elif p==None and q!=None:
            return False
        elif p!=None and q!=None and p.val!=q.val:
            return False
        else:
            return self.isSameTree(p.left,q.left) and self.isSameTree(p.right,q.right)