# 12.06.2023 [228. Summary Ranges]

Fold continues ranges in a sorted array `1 2 3 5` -> `1->3, 5`

12.06.2023

228. Summary Ranges easy
blog post

Problem TLDR

Fold continues ranges in a sorted array 1 2 3 5 -> 1->3, 5

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https://t.me/leetcode_daily_unstoppable/243

Intuition

Scan from start to end, modify the last interval or add a new one.

Approach

Let’s write a Kotlin one-liner

Complexity

• Time complexity:
  O(n)

• Space complexity:
  O(n)

Code

fun summaryRanges(nums: IntArray): List<String> = nums
    .fold(mutableListOf<IntArray>()) { r, t ->
        if (r.isEmpty() || r.last()[1] + 1 < t) r += intArrayOf(t, t)
        else r.last()[1] = t
        r
    }
    .map { (f, t) -> if (f == t) "$f" else "$f->$t"}