# 1056. Confusing Number 易混淆数

@TOC

## # 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:

1. 0 <= N <= 10^9
2. After the rotation we can ignore leading zeros, for example if after rotation we have 0008 then this number is considered as just 8.

## # 解题方法

### # 字典

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