leetcode 226. Invert Binary Tree 题解

226. Invert Binary Tree

提交网址： https://leetcode.com/problems/invert-binary-tree/

Total Accepted: 84040 Total Submissions: 186266 Difficulty: Easy  ACrate:45.1%

Invert a binary tree.

     4
   /   \
  2     7
 / \   / \
1   3 6   9

     to

     4
   /   \
  7     2
 / \   / \
9   6 3   1

Trivia:
This problem was inspired by this original tweet by Max Howell:

Google: 90% of our engineers use the software you wrote (Homebrew), but you can’t invert a binary tree on a whiteboard so fuck off.

AC代码: 

#include<cstdio>
#include<iostream>
using namespace std;
 
struct TreeNode {
     int val;
     TreeNode *left;
     TreeNode *right;
     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 };
 
class Solution {
public:
    TreeNode* invertTree(TreeNode* root) {
        if(root==NULL) return NULL;
        TreeNode* p;

        p=root->left;
        root->left=root->right;
        root->right=p;             // 和实现两个变量的交换接近
         
        invertTree(root->left);
        invertTree(root->right);
        return root;
    }
};
 
// 以下为验证
/*
int main() {
    TreeNode *root = new TreeNode(-1);
    TreeNode *temp;
    root->left = new TreeNode(2);
    root->right = new TreeNode(3);
    root->right->right = new TreeNode(0);
 
    Solution sol;
 
    cout << root->left->val << endl;
    temp=sol.invertTree(root);
    cout << temp->left->val << endl;
    cout << temp->left->left->val << endl;
         
    return 0;
}*/

在线测试是以满二叉树为例的(总的结点数需要为：2 ⁿ -1，比如下图以 3个为例...)