LeetCode Entry

1980. Find Unique Binary String

08.03.2026 medium 2026 kotlin rust

Uniq bits not in a set

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Problem TLDR

Uniq bits not in a set #medium

Intuition

Brute-force, only 16 elements. Max count is 2^16. Max count where first new appears is n+1. Cantour trick: build a new uniq by flipping exactly one uniq bit position in all bits. It would be uniq because it differs at least by one bit with each in a set.

Approach

• xor trick “1” converts to “0”, because they even-odd

Complexity

• Time complexity: \(O(n)\)

• Space complexity: \(O(n)\)

Code

// 12ms
    fun findDifferentBinaryString(n: Array<String>) =
    n.mapIndexed{i,s -> 1-(s[i]-'0')}.joinToString("")
    //n.indices.joinToString(""){""+"10"[n[it][it]-'0']}
    //(0..16).map{it.toString(2).padStart(n.size,'0')}.find{it !in n}
    //(0..16).first{it !in n.map{it.toInt(2)}}.toString(2).padStart(n.size,'0')

// 0ms
    pub fn find_different_binary_string(n: Vec<String>) -> String {
       (0..n.len()).map(|i| (n[i].as_bytes()[i]^1)as char).join("")
    }