第六周Same Tree

Same Tree

Leetcode algorithms problem 100：Same Tree

• 问题描述

  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.

• 问题提示

  无

• 思路

  使用递归，首先返回节点为NULL时的相等情况；两个节点都是有效指针时，如果根值不一样，返回false，一样则进入递归：根的左侧树是相同的（递归）&&根的右侧树是相同的（递归），否则返回false

代码

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

时间复杂度: O(n)
空间复杂度: O(2^n)

---