LeetCode Entry

976. Largest Perimeter Triangle

28.09.2025 easy 2025 kotlin rust

Max triangle perimeter from array of lengths window

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Problem TLDR

Max triangle perimeter from array of lengths #easy #sliding_window

Intuition

Sort. Consider every 3-sliding window from biggest: when a+b <= c move next, discard the c, otherwise finish. When c is bigger than closes a+b, then it will be bigger than any other pair sum.

Approach

  • this is not an easy problem

Complexity

  • Time complexity: \(O(nlog(n))\)

  • Space complexity: \(O(n)\) or O(1)

Code


// 81ms
    fun largestPerimeter(n: IntArray) =
        max(0, n.sorted().windowed(3)
        .maxOf{(a,b,c) -> (a+b+c)*(a+b).compareTo(c)})



// 0ms
    pub fn largest_perimeter(n: Vec<i32>) -> i32 {
        n.iter().sorted_by_key(|&x|-x).tuple_windows()
        .find(|&(c,b,a)| a+b>*c).map_or(0, |(a,b,c)| a+b+c)
    }