Confusing Number — LeetCode 1056 Python Solution

The problem

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.

Example

Input

n = 6

Output

true

Explanation

We get 9 after rotating 6, 9 is a valid number, and 9 != 6.

Python solution

class Solution:
    def confusingNumber(self, n: int) -> bool:
        x, y = n, 0
        d = [0, 1, -1, -1, -1, -1, 9, -1, 8, 6]
        while x:
            x, v = divmod(x, 10)
            if d[v] < 0:
                return False
            y = y * 10 + d[v]
        return y != n

Complexity

Pattern: Math and Number Theory

Find the closed form, the invariant, or the modular identity — and skip the loop entirely. LeetCode 1056. Confusing Number is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Math.

The math and number theory guide has the Python template for the pattern and the 485 LeetCode problems that use it.

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