【Leetcode】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：对两棵树进行遍历即可，这里采用先序遍历的方法。

代码：

/**
 * 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) {
        return PrerderTraverse(p,q);
    }
    
private:
    bool PrerderTraverse(TreeNode *p, TreeNode *q){
        if(p==nullptr&&q==nullptr)return true;
        if(p==nullptr||q==nullptr)return false;
        if(p->val!=q->val){
            return false;
        }else{
            return PrerderTraverse(p->left,q->left)&&PrerderTraverse(p->right,q->right);
        }
    }
};

可以将先序遍历部分写的更加简洁：

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