LeetCode in Kotlin

1313. Decompress Run-Length Encoded List

Easy

We are given a list nums of integers representing a list compressed with run-length encoding.

Consider each adjacent pair of elements [freq, val] = [nums[2*i], nums[2*i+1]] (with i >= 0). For each such pair, there are freq elements with value val concatenated in a sublist. Concatenate all the sublists from left to right to generate the decompressed list.

Return the decompressed list.

Example 1:

Input: nums = [1,2,3,4]

Output: [2,4,4,4]

Explanation: The first pair [1,2] means we have freq = 1 and val = 2 so we generate the array [2].

The second pair [3,4] means we have freq = 3 and val = 4 so we generate [4,4,4].

At the end the concatenation [2] + [4,4,4] is [2,4,4,4].

Example 2:

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

Output: [1,3,3]

Constraints:

• 2 <= nums.length <= 100
• nums.length % 2 == 0
• 1 <= nums[i] <= 100

Solution

class Solution {
    fun decompressRLElist(nums: IntArray): IntArray {
        var len = 0
        run {
            var i = 0
            while (i < nums.size) {
                len += nums[i]
                i += 2
            }
        }
        val ans = IntArray(len)
        var index = 0
        var i = 0
        while (i < nums.size) {
            var j = nums[i]
            while (j > 0) {
                ans[index] = nums[i + 1]
                index++
                j--
            }
            i += 2
        }
        return ans
    }
}

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