confusing_number.cpp

/*
1056. Confusing Number
Easy

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
*/

class Solution {
public:
    bool confusingNumber(int N) {
        if(N==0) return false;
        int num = N, sum=0, p=log(N)/log(10);
        while(num!=0){
            int pop = num%10;
            num/=10;
            if(pop==2 || pop==3|| pop==4|| pop==5|| pop==7)
                return false;
            if(pop==6)
                sum+=9*pow(10,p);
            else if(pop==9)
                sum+=6*pow(10,p);
            else if(pop==0 || pop==1||pop==8)
                sum+=pop*pow(10,p);
            p--;
        }
        if(sum==N) return false;
        return true;
    }
};