LeetCode in Kotlin

2948. Make Lexicographically Smallest Array by Swapping Elements

Medium

You are given a 0-indexed array of positive integers nums and a positive integer limit.

In one operation, you can choose any two indices i and j and swap nums[i] and nums[j] if |nums[i] - nums[j]| <= limit.

Return the lexicographically smallest array that can be obtained by performing the operation any number of times.

An array a is lexicographically smaller than an array b if in the first position where a and b differ, array a has an element that is less than the corresponding element in b. For example, the array [2,10,3] is lexicographically smaller than the array [10,2,3] because they differ at index 0 and 2 < 10.

Example 1:

Input: nums = [1,5,3,9,8], limit = 2

Output: [1,3,5,8,9]

Explanation: Apply the operation 2 times:

• Swap nums[1] with nums[2]. The array becomes [1,3,5,9,8]

• Swap nums[3] with nums[4]. The array becomes [1,3,5,8,9]

We cannot obtain a lexicographically smaller array by applying any more operations.

Note that it may be possible to get the same result by doing different operations.

Example 2:

Input: nums = [1,7,6,18,2,1], limit = 3

Output: [1,6,7,18,1,2]

Explanation: Apply the operation 3 times:

• Swap nums[1] with nums[2]. The array becomes [1,6,7,18,2,1]

• Swap nums[0] with nums[4]. The array becomes [2,6,7,18,1,1]

• Swap nums[0] with nums[5]. The array becomes [1,6,7,18,1,2]

We cannot obtain a lexicographically smaller array by applying any more operations.

Example 3:

Input: nums = [1,7,28,19,10], limit = 3

Output: [1,7,28,19,10]

Explanation: [1,7,28,19,10] is the lexicographically smallest array we can obtain because we cannot apply the operation on any two indices.

Constraints:

• 1 <= nums.length <= 105
• 1 <= nums[i] <= 109
• 1 <= limit <= 109

Solution

import kotlin.math.abs

class Solution {
    fun lexicographicallySmallestArray(nums: IntArray, limit: Int): IntArray {
        val n = nums.size
        val nodes = Array(n) { i -> Node(i, nums[i]) }
        nodes.sortWith { a: Node, b: Node ->
            Integer.signum(
                a.value - b.value,
            )
        }
        var group = 1
        nodes[0].group = group
        for (i in 1 until n) {
            if (abs(nodes[i].value - nodes[i - 1].value) <= limit) {
                nodes[i].group = group
            } else {
                nodes[i].group = ++group
            }
        }
        val groupBase = IntArray(group + 1)
        for (i in n - 1 downTo 0) {
            groupBase[nodes[i].group] = i
        }
        val groupIndex = IntArray(n)
        for (node in nodes) {
            groupIndex[node.id] = node.group
        }
        val ans = IntArray(n)
        for (i in 0 until n) {
            val index = groupBase[groupIndex[i]]
            ans[i] = nodes[index].value
            groupBase[groupIndex[i]]++
        }
        return ans
    }

    private class Node(var id: Int, var value: Int) {
        var group: Int = 0
    }
}

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