LeetCode Entry

3761. Minimum Absolute Distance Between Mirror Pairs

17.04.2026 medium 2026 kotlin rust

Distance to prev mirror number

3761. Minimum Absolute Distance Between Mirror Pairs medium substack youtube

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Problem TLDR

Distance to prev mirror number #medium

Intuition

Use a hashmap, scan, put mirrors into map, check for current number.

Approach

• Kotlin: string conversion is shorter
• Rust: (0..).zip(n), filter_map

Complexity

• Time complexity: \(O(m)\)

• Space complexity: \(O(n)\)

Code

// 232ms
    fun minMirrorPairDistance(n: IntArray) = HashMap<Int, Int>().let { m ->
        n.indices.minOf { i ->
            i - (m[n[i]] ?: -n.size).also { m["${n[i]}".reversed().toInt()] = i }
        }.takeIf { it < n.size } ?: -1
    }

// 19ms
    pub fn min_mirror_pair_distance(n: Vec<i32>) -> i32 {
        let mut m = HashMap::new();
        (0..).zip(n).filter_map(|(i, mut x)| {
            let d = m.get(&x).map(|j| i-j);
            let mut r = 0; while x > 0 {r = r*10+x%10; x /= 10}
            m.insert(r, i); d
        }).min().unwrap_or(-1)
    }