LeetCode in Kotlin

3070. Count Submatrices with Top-Left Element and Sum Less Than k

Medium

You are given a 0-indexed integer matrix grid and an integer k.

Return the number of submatrices that contain the top-left element of the grid, and have a sum less than or equal to k.

Example 1:

Input: grid = [[7,6,3],[6,6,1]], k = 18

Output: 4

Explanation: There are only 4 submatrices, shown in the image above, that contain the top-left element of grid, and have a sum less than or equal to 18.

Example 2:

Input: grid = [[7,2,9],[1,5,0],[2,6,6]], k = 20

Output: 6

Explanation: There are only 6 submatrices, shown in the image above, that contain the top-left element of grid, and have a sum less than or equal to 20.

Constraints:

• m == grid.length
• n == grid[i].length
• 1 <= n, m <= 1000
• 0 <= grid[i][j] <= 1000
• 1 <= k <= 109

Solution

class Solution {
    fun countSubmatrices(grid: Array<IntArray>, k: Int): Int {
        val n = grid[0].size
        val sums = IntArray(n)
        var ans = 0
        for (ints in grid) {
            var sum = 0
            for (col in 0 until n) {
                sum += ints[col]
                sums[col] += sum
                if (sums[col] <= k) {
                    ans++
                } else {
                    break
                }
            }
        }
        return ans
    }
}

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