1056. Confusing Number

A confusing number is a number that when rotated 180 degrees becomes a different number with each digit valid.

We can rotate digits of a number by 180 degrees to form new digits.

• When 0, 1, 6, 8, and 9 are rotated 180 degrees, they become 0, 1, 9, 8, and 6 respectively.
• When 2, 3, 4, 5, and 7 are rotated 180 degrees, they become invalid.

Note that after rotating a number, we can ignore leading zeros.

• For example, after rotating 8000, we have 0008 which is considered as just 8.

Given an integer n, return true if it is a confusing number, or false otherwise.

class Solution {
public:
    bool confusingNumber(int n) {
        int N = n, rev = 0;
        unordered_set<int> bad{2,3,4,5,7};
        while(N) {
            int d = N % 10;
            N /= 10;
            if(bad.count(d)) return false;
            if(d == 6) d = 9;
            else if(d == 9) d = 6;
            rev = rev * 10 + d;
        }
        return n != rev;
    }
};