1056. Confusing Number

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.

Rust Solution

struct Solution;

impl Solution {
    fn rotate(d: i32) -> Option<i32> {
        match d {
            0 => Some(0),
            1 => Some(1),
            6 => Some(9),
            8 => Some(8),
            9 => Some(6),
            _ => None,
        }
    }

    fn confusing_number(mut n: i32) -> bool {
        let num = n;
        let mut rev = 0;
        while n > 0 {
            let d = n % 10;
            if let Some(t) = Self::rotate(d) {
                rev *= 10;
                rev += t;
                n /= 10;
            } else {
                return false;
            }
        }
        rev != num
    }
}

#[test]
fn test() {
    assert_eq!(Solution::confusing_number(6), true);
    assert_eq!(Solution::confusing_number(89), true);
    assert_eq!(Solution::confusing_number(11), false);
    assert_eq!(Solution::confusing_number(25), false);
}

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