【LeetCode】1056. Confusing Number 解题报告(C++)

作者：负雪明烛
id： fuxuemingzhu
个人博客：http://fuxuemingzhu.cn/

题目描述

Given a number N, return true if and only if it is a confusing number, which satisfies the following condition:

We can rotate digits by 180 degrees to form new digits. When 0, 1, 6, 8, 9 are rotated 180 degrees, they become 0, 1, 9, 8, 6 respectively. When 2, 3, 4, 5 and 7 are rotated 180 degrees, they become invalid. A confusing number is a number that when rotated 180 degrees becomes a different number with each digit valid.

Example 1:

Input: 6
Output: true
Explanation:
We get 9 after rotating 6, 9 is a valid number and 9!=6.

Example 2:

Input: 89
Output: true
Explanation:
We get 68 after rotating 89, 86 is a valid number and 86!=89.

Example 3:

Input: 11
Output: false
Explanation:
We get 11 after rotating 11, 11 is a valid number but the value remains the same, thus 11 is not a confusing number.

Example 4:

Input: 25
Output: false
Explanation:
We get an invalid number after rotating 25.

Note:

0 <= N <= 10^9
After the rotation we can ignore leading zeros, for example if after rotation we have 0008 then this number is considered as just 8.

题目大意

给定一个数字 N，当它满足以下条件的时候返回 true：
原数字旋转 180° 以后可以得到新的数字。
如 0, 1, 6, 8, 9 旋转 180° 以后，得到了新的数字 0, 1, 9, 8, 6 。
2, 3, 4, 5, 7 旋转 180° 后，得到的不是数字。
易混淆数 (confusing number) 在旋转180°以后，可以得到和原来不同的数，且新数字的每一位都是有效的。

解题方法

字典

使用字典保存每个可以翻转的字符翻转后会变成谁，然后对每一位数字进行翻转，看翻转后的数字和原来的数字是否相等。

C++代码如下：

class Solution {public:bool confusingNumber(int N) {unordered_map<int, int> m{{0, 0}, {1, 1}, {6, 9}, {8, 8}, {9, 6}};int rotate = 0;int temp = N;while (temp != 0) {int mod = temp % 10;if (!m.count(mod))return false;rotate = 10 * rotate + m[mod];temp /= 10;}return rotate != N;}
};

日期

2019 年 9 月 18 日 —— 今日又是九一八