1056. Confusing Number

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1056. Confusing Number

Description

Difficulty: Easy

Related Topics: Math

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.

Example 1:

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Input: n = 6
Output: true
Explanation: We get 9 after rotating 6, 9 is a valid number, and 9 != 6.

Example 2:

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Input: n = 89
Output: true
Explanation: We get 68 after rotating 89, 68 is a valid number and 68 != 89.

Example 3:

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Input: n = 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

Constraints:

  • 0 <= n <= 109

Hints/Notes

  • No need to do the mapping, we can use switch during the loop

Solution

Language: C++

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class Solution {
public:
    bool confusingNumber(int n) {
        int sum = 0, tmp = n;
        while (tmp > 0) {
            int r = tmp % 10;
            tmp /= 10;
            switch(r) {
                case 0:
                case 1:
                case 8:
                    sum = sum * 10 + r;
                    break;
                case 6:
                    sum = sum * 10 + 9;
                    break;
                case 9:
                    sum = sum * 10 + 6;
                    break;
                case 2:
                case 3:
                case 4:
                case 5:
                case 7:
                    return false;
            }
        }
        return !(sum == n);
    }
};