LeetCode in Kotlin

1432. Max Difference You Can Get From Changing an Integer

Medium

You are given an integer num. You will apply the following steps exactly two times:

• Pick a digit x (0 <= x <= 9).
• Pick another digit y (0 <= y <= 9). The digit y can be equal to x.
• Replace all the occurrences of x in the decimal representation of num by y.
• The new integer cannot have any leading zeros, also the new integer cannot be 0.

Let a and b be the results of applying the operations to num the first and second times, respectively.

Return the max difference between a and b.

Example 1:

Input: num = 555

Output: 888

Explanation: The first time pick x = 5 and y = 9 and store the new integer in a.

The second time pick x = 5 and y = 1 and store the new integer in b.

We have now a = 999 and b = 111 and max difference = 888

Example 2:

Input: num = 9

Output: 8

Explanation: The first time pick x = 9 and y = 9 and store the new integer in a.

The second time pick x = 9 and y = 1 and store the new integer in b.

We have now a = 9 and b = 1 and max difference = 8

Constraints:

• 1 <= num <= 10⁸

Solution

import java.util.ArrayDeque
import java.util.Deque

@Suppress("NAME_SHADOWING")
class Solution {
    fun maxDiff(num: Int): Int {
        var num = num
        val stack: Deque<Int> = ArrayDeque()
        var xMax = 9
        val yMax = 9
        var xMin = 0
        var yMin = 0
        var min = 0
        var max = 0
        var areDigitsUnique = true
        while (num != 0) {
            if (stack.isNotEmpty() && num % 10 != stack.peek()) {
                areDigitsUnique = false
            }
            stack.push(num % 10)
            num /= 10
            if (stack.peek() != 9) {
                xMax = stack.peek()
            }
            if (stack.peek() > 1) {
                xMin = stack.peek()
            }
        }
        if (areDigitsUnique || stack.peek() == xMin) {
            // Handles no leading zeros/non zero constraints.
            yMin = 1
        }
        while (stack.isNotEmpty()) {
            min = min * 10 + if (stack.peek() == xMin) yMin else stack.peek()
            max = max * 10 + if (stack.peek() == xMax) yMax else stack.peek()
            stack.pop()
        }
        return max - min
    }
}

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