LeetCode Entry

961. N-Repeated Element in Size 2N Array

02.01.2026 easy 2026 kotlin rust

Duplicate majority element

961. N-Repeated Element in Size 2N Array easy blog post substack youtube

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Problem TLDR

Duplicate majority element #easy

Intuition

The easy intuition is just to count frequencies.

Approach

• frequency of 2 is enough
• if first element skipped then majority voting solution applicable
• another fun solution is to look at sum and uniq’s sum

Complexity

• Time complexity: \(O(n)\)

• Space complexity: \(O(1)\)

Code

// 35ms
    fun repeatedNTimes(n: IntArray) =
        (n.sum() - n.toSet().sum())/(n.size/2-1)

// 0ms
    pub fn repeated_n_times(n: Vec<i32>) -> i32 {
        let (mut j, mut f) = (0, 0);
        n[(1..n.len()).find(|&i| {
            if f == 0 { j = i }
            f += (n[0]==n[i]||n[i]==n[j]) as i32 * 2 -1; f > 1
        }).unwrap_or(j)]
    }