LeetCode Entry

3507. Minimum Pair Removal to Sort Array I

22.01.2026 easy 2026 kotlin rust

Sort by removing lowest sum pairs

3507. Minimum Pair Removal to Sort Array I easy blog post substack youtube

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Problem TLDR

Sort by removing lowest sum pairs #easy

Intuition

Simulate the process.

Approach

• just create a new array each time
• or in Rust we can actually remove by index in-place

Complexity

• Time complexity: \(O(n^2)\) n^2log(n) for golfing in Kotlin

• Space complexity: \(O(n)\)

Code

// 76ms
    fun minimumPairRemoval(l: IntArray): Int {
        val l = l.toList()
        if (l == l.sorted()) return 0
        val j = (1..<l.size).minBy { l[it-1] + l[it] }
        return 1 + minimumPairRemoval((l.take(j-1) + (l[j-1]+l[j]) + l.drop(j+1)).toIntArray())
    }

// 0ms
    pub fn minimum_pair_removal(mut l: Vec<i32>) -> i32 {
        (0..).find(|_| {
            let ok = l.windows(2).all(|w| w[0] <= w[1]);
            if let Some(j) = (1..l.len()).min_by_key(|&i| l[i-1] + l[i]) { l[j-1] += l[j];  l.remove(j); }
            ok
        }).unwrap()
    }