LeetCode Entry

3741. Minimum Distance Between Three Equal Elements II

11.04.2026 medium 2026 kotlin rust

Min sum of distances between i,j,k of the same values

3741. Minimum Distance Between Three Equal Elements II medium substack youtube

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Problem TLDR

Min sum of distances between i,j,k of the same values #medium

Intuition

Same as yesterday: keep two previous indices. Sum of abs (i,j,k) is 2*(i-k).

     fun minimumDistance(n: IntArray) = n
        .indices.groupBy{n[it]}.values
        .flatMap { it.windowed(3) { 2 * (it[2]-it[0])}}
        .minOrNull() ?: -1

    pub fn minimum_distance(n: Vec<i32>) -> i32 {
        (0..n.len()).into_group_map_by(|&i| n[i]).values()
        .flat_map(|v| v.windows(3).map(|w|2*(w[2]-w[0]) as i32))
        .min().unwrap_or(-1)
    }

Approach

• let’s write optimized versions
• my yesterday golfed solutiona are also accepted

Complexity

• Time complexity: \(O(n)\)

• Space complexity: \(O(n)\)

Code

// 85ms
    fun minimumDistance(n: IntArray) =
        LongArray(100001){-1}.let { p -> n.indices.minOf { i ->
            val j = p[n[i]]; p[n[i]] = j shl 32 or 1L*i
            if (j >= 0) 2L*(i-(j shr 32)) else Long.MAX_VALUE
        }.takeIf { it < Long.MAX_VALUE } ?: -1L }

// 16ms
    pub fn minimum_distance(n: Vec<i32>) -> i32 {
        let mut p = [-1i64; 100001];
        (0..n.len()).filter_map(|i| {
            let j = p[n[i] as usize]; p[n[i] as usize] = j<<32|i as i64;
            (j >= 0).then(|| 2*(i as i64 - (j>>32)) as i32)
        }).min().unwrap_or(-1)
    }