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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.

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

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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;
    }
}

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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));
    }
};

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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
}

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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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