add new solutions

solutions/36/q3643/solution.go

@@ -0,0 +1,19 @@
+// Package q3643 implements a solution for https://leetcode.com/problems/flip-square-submatrix-vertically/
+package q3643
+
+func reverseSubmatrix(grid [][]int, x int, y int, k int) [][]int {
+	x, y = y, x // lol
+	swapBuf := make([]int, k)
+
+	for i := range k / 2 {
+		y1 := y + i
+		y2 := y + k - 1 - i
+
+		copy(swapBuf, grid[y1][x:x+k])
+		copy(grid[y1][x:x+k], grid[y2][x:x+k])
+		copy(grid[y2][x:x+k], swapBuf)
+	}
+	return grid
+}
+
+var _ = reverseSubmatrix