LeetCode Entry

1337. The K Weakest Rows in a Matrix

18.09.2023 easy 2023 kotlin

k indices with smallest row sum in a binary matrix

1337. The K Weakest Rows in a Matrix easy blog post substack

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Problem TLDR

k indices with smallest row sum in a binary matrix

Intuition

We can precompute row sums, then use a Priority Queue to find k smallest. However, just sorting all will also work.

Approach

Let’s use Kotlin’s collections API

• map
• filter
• sortedBy https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/sorted-by.html
• take
• toIntArray

Complexity

• Time complexity: \(O(n^2logn)\)

• Space complexity: \(O(n^2)\)

Code

    fun kWeakestRows(mat: Array<IntArray>, k: Int) = mat
        .map { it.filter { it == 1 }.sum() ?: 0 }
        .withIndex()
        .sortedBy { it.value }
        .map { it.index }
        .take(k)
        .toIntArray()