LeetCode in Kotlin

2121. Intervals Between Identical Elements

Medium

You are given a 0-indexed array of n integers arr.

The interval between two elements in arr is defined as the absolute difference between their indices. More formally, the interval between arr[i] and arr[j] is |i - j|.

Return an array intervals of length n where intervals[i] is the sum of intervals between arr[i] and each element in arr with the same value as arr[i].

Note: |x| is the absolute value of x.

Example 1:

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

Output: [4,2,7,2,4,4,5]

Explanation:

• Index 0: Another 2 is found at index 4. |0 - 4| = 4

• Index 1: Another 1 is found at index 3. |1 - 3| = 2

• Index 2: Two more 3s are found at indices 5 and 6. |2 - 5| + |2 - 6| = 7

• Index 3: Another 1 is found at index 1. |3 - 1| = 2

• Index 4: Another 2 is found at index 0. |4 - 0| = 4

• Index 5: Two more 3s are found at indices 2 and 6. |5 - 2| + |5 - 6| = 4

• Index 6: Two more 3s are found at indices 2 and 5. |6 - 2| + |6 - 5| = 5

Example 2:

Input: arr = [10,5,10,10]

Output: [5,0,3,4]

Explanation:

• Index 0: Two more 10s are found at indices 2 and 3. |0 - 2| + |0 - 3| = 5

• Index 1: There is only one 5 in the array, so its sum of intervals to identical elements is 0.

• Index 2: Two more 10s are found at indices 0 and 3. |2 - 0| + |2 - 3| = 3

• Index 3: Two more 10s are found at indices 0 and 2. |3 - 0| + |3 - 2| = 4

Constraints:

• n == arr.length
• 1 <= n <= 105
• 1 <= arr[i] <= 105

Solution

class Solution {
    fun getDistances(arr: IntArray): LongArray {
        val n = arr.size
        val map: MutableMap<Int, MutableList<Int>> = HashMap()
        for (i in 0 until n) {
            var list = map[arr[i]]
            if (list == null) {
                list = ArrayList()
            }
            list.add(i)
            map[arr[i]] = list
        }
        val ans = LongArray(n)
        ans.fill(0)
        for (list in map.values) {
            var sum: Long = 0
            val first = list[0]
            for (i in 1 until list.size) {
                sum = sum + list[i] - first
            }
            ans[first] = sum
            var prevElements = 0
            var nextElements = list.size - 2
            for (i in 1 until list.size) {
                val diff = list[i] - list[i - 1]
                sum = sum + diff.toLong() * (prevElements - nextElements)
                ans[list[i]] = sum
                prevElements++
                nextElements--
            }
        }
        return ans
    }
}

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