kt: add «1277. Count Square Submatrices with All Ones»

URL:	https://leetcode.com/problems/count-square-submatrices-with-all-ones/
Signed-off-by: Matej Focko <me@mfocko.xyz>

kt/count-square-submatrices-with-all-ones.kt

@@ -0,0 +1,26 @@
+class Solution {
+    fun <A, B> product(
+        xs: Sequence<A>,
+        ys: Sequence<B>,
+    ): Sequence<Pair<A, B>> = xs.flatMap { x -> ys.map { y -> x to y } }
+
+    fun <A, B> product(
+        xs: Iterable<A>,
+        ys: Iterable<B>,
+    ): Sequence<Pair<A, B>> = product(xs.asSequence(), ys.asSequence())
+
+    fun countSquares(matrix: Array<IntArray>): Int {
+        val (rows, columns) = matrix.size to matrix[0].size
+        val dp = Array(rows + 1) { IntArray(columns + 1) }
+
+        var answer = 0
+        for ((y, x) in product(0..<rows, 0..<columns).filter { (y, x) ->
+            matrix[y][x] == 1
+        }) {
+            dp[y + 1][x + 1] = 1 + listOf(dp[y][x + 1], dp[y + 1][x], dp[y][x]).min()
+            answer += dp[y + 1][x + 1]
+        }
+
+        return answer
+    }
+}