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3783. Mirror Distance of an Integer

Description

You are given an integer n.

Define its mirror distance as: abs(n - reverse(n))​​​​​​​ where reverse(n) is the integer formed by reversing the digits of n.

Return an integer denoting the mirror distance of n​​​​​​​.

abs(x) denotes the absolute value of x.

 

Example 1:

Input: n = 25

Output: 27

Explanation:

  • reverse(25) = 52.
  • Thus, the answer is abs(25 - 52) = 27.

Example 2:

Input: n = 10

Output: 9

Explanation:

  • reverse(10) = 01 which is 1.
  • Thus, the answer is abs(10 - 1) = 9.

Example 3:

Input: n = 7

Output: 0

Explanation:

  • reverse(7) = 7.
  • Thus, the answer is abs(7 - 7) = 0.

 

Constraints:

  • 1 <= n <= 109

Solutions

Solution 1: Simulation

We define a function $\text{reverse}(x)$ to reverse the digits of integer $x$. Specifically, we initialize a variable $y$ to $0$, then repeatedly append the last digit of $x$ to the end of $y$, and remove the last digit from $x$, until $x$ becomes $0$. Finally, $y$ is the reversed integer.

Next, we compute the mirror distance of integer $n$, which is $\text{abs}(n - \text{reverse}(n))$, and return the result.

The time complexity is $O(\log n)$ and the space complexity is $O(1)$, where $n$ is the size of the input integer.

  • class Solution {
    public int mirrorDistance(int n) {
        return Math.abs(n - reverse(n));
    }

    private int reverse(int x) {
        int y = 0;
        for (; x > 0; x /= 10) {
            y = y * 10 + x % 10;
        }
        return y;
    }
}


  • class Solution {
public:
    int mirrorDistance(int n) {
        auto reverse = [](int x) -> int {
            int y = 0;
            for (; x; x /= 10) {
                y = y * 10 + x % 10;
            }
            return y;
        };
        return abs(n - reverse(n));
    }
};


  • class Solution:
    def mirrorDistance(self, n: int) -> int:
        return abs(n - int(str(n)[::-1]))


  • func mirrorDistance(n int) int {
	reverse := func(x int) int {
		y := 0
		for ; x > 0; x /= 10 {
			y = y*10 + x%10
		}
		return y
	}
	return abs(n - reverse(n))
}

func abs(x int) int {
	if x < 0 {
		return -x
	}
	return x
}


  • function mirrorDistance(n: number): number {
    const reverse = (x: number): number => {
        let y = 0;
        for (; x > 0; x = Math.floor(x / 10)) {
            y = y * 10 + (x % 10);
        }
        return y;
    };
    return Math.abs(n - reverse(n));
}

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