LeetCode [1056] Confusing Number

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:

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.

class Solution {
    Map<Integer, Integer> map = new HashMap<>();
    public boolean confusingNumber(int N) {
        map.put(0,0);
        map.put(1,1);
        map.put(6,9);
        map.put(8,8);
        map.put(9,6);
        int t = N;
        int r = 0;
        while(t>0){
            int v = t%10;
            t = t/10;
            if(!map.containsKey(v)) return false;
            int u = map.get(v);
            r = r*10+u;
        }
        
        return r!=N;
    }
}