LeetCode in Kotlin

1282. Group the People Given the Group Size They Belong To

Medium

There are n people that are split into some unknown number of groups. Each person is labeled with a unique ID from 0 to n - 1.

You are given an integer array groupSizes, where groupSizes[i] is the size of the group that person i is in. For example, if groupSizes[1] = 3, then person 1 must be in a group of size 3.

Return a list of groups such that each person i is in a group of size groupSizes[i].

Each person should appear in exactly one group, and every person must be in a group. If there are multiple answers, return any of them. It is guaranteed that there will be at least one valid solution for the given input.

Example 1:

Input: groupSizes = [3,3,3,3,3,1,3]

Output: [[5],[0,1,2],[3,4,6]]

Explanation:

The first group is [5]. The size is 1, and groupSizes[5] = 1.

The second group is [0,1,2]. The size is 3, and groupSizes[0] = groupSizes[1] = groupSizes[2] = 3.

The third group is [3,4,6]. The size is 3, and groupSizes[3] = groupSizes[4] = groupSizes[6] = 3.

Other possible solutions are [[2,1,6],[5],[0,4,3]] and [[5],[0,6,2],[4,3,1]].

Example 2:

Input: groupSizes = [2,1,3,3,3,2]

Output: [[1],[0,5],[2,3,4]]

Constraints:

• groupSizes.length == n
• 1 <= n <= 500
• 1 <= groupSizes[i] <= n

Solution

class Solution {
    fun groupThePeople(groupSizes: IntArray): List<List<Int>> {
        val map: MutableMap<Int, MutableList<Int>> = HashMap()
        for (i in groupSizes.indices) {
            val list = map.getOrDefault(groupSizes[i], ArrayList())
            list.add(i)
            map[groupSizes[i]] = list
        }
        val result: MutableList<List<Int>> = ArrayList()
        for ((key, list) in map) {
            var i = 0
            do {
                result.add(list.subList(i, i + key))
                i += key
            } while (i + key <= list.size)
        }
        return result
    }
}

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