LeetCode Entry

3863. Minimum Operations to Sort a String

21.10.2026 medium 2026 kotlin rust

Ops to sort by sorting substrings

3863. Minimum Operations to Sort a String medium substack youtube

https://dmitrysamoylenko.com/leetcode/

Join me on Telegram

https://t.me/leetcode_daily_unstoppable/1518

Problem TLDR

Ops to sort by sorting substrings

Intuition

Brain teaser of corner cases. 0 if sorted 1 if first is min or last is first max -1 if two unsorted 3 if last is min and first is last max 2 otherwise

Approach

• passed after 6 failed attempts

Complexity

• Time complexity: \(O(nlong)\)

• Space complexity: \(O(n)\)

Code

    fun minOperations(s: String) = s.run{when {
        toList() == toList().sorted() -> 0
        first() == min() || last() == max() -> 1
        length < 3 -> -1
        indexOf(min()) == length-1 && lastIndexOf(max()) < 1 -> 3
        else -> 2
    }}

    pub fn min_operations(s: String) -> i32 {
        let MinMax(min, max) = s.chars().minmax() else { return 0 };
        s.as_bytes().is_sorted().then_some(0)
            .or_else(|| (s.starts_with(min) || s.ends_with(max)).then_some(1))
            .or_else(|| (s.len() < 3).then_some(-1))
            .or_else(|| (s.rfind(max)==Some(0) && s.find(min)==Some(s.len()-1)).then_some(3))
            .unwrap_or(2)
    }