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Leetcode#100. Same Tree(判断两个二叉树相同)

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.

题意

给你两个二叉树p和q,写一个函数判断是否相同。

两个二叉树完全相同即结构,结点和结点的值也相同。

分析

递归的应用,分析递归模型

  • p和q都为空,返回true。
  • p和q其中一个为空,返回false。
  • p和q不同为空且p和q对应的值相同为true,不同为false。
  • 其他情况,返回false。

C++语言

/**
 * 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) 
    {
        bool like1,like2;
        //同为空
        if( p==NULL && q==NULL)
            return true;
        //其中一个为空
        else if(p == NULL || q==NULL)
            return false;
        else if(p->val == q->val)
        {
            like1 = isSameTree(p->left,q->left);
            like2 = isSameTree(p->right,q->right);
            return (like1&&like2);
        }
        else
            return false;
    }
};
           

Python语言

# 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):

        if p == None and q == None:
            return True
        elif p == None or q == None:
            return False
        elif p.val == q.val:
            like1 = self.isSameTree(p.left,q.left)
            like2 = self.isSameTree(p.right,q.right)
            return like1 and like2
        else:
            return False