go: add «2326. Spiral Matrix IV»

Signed-off-by: Matej Focko <me@mfocko.xyz>

go/spiral-matrix-iv.go

@@ -0,0 +1,39 @@
+package main
+
+const (
+	UNSET int = -1
+)
+
+func spiralMatrix(m int, n int, node *ListNode) [][]int {
+	matrix := make([][]int, m)
+	for y := 0; y < m; y++ {
+		matrix[y] = make([]int, n)
+		for x := 0; x < n; x++ {
+			matrix[y][x] = UNSET
+		}
+	}
+
+	Next := func(dy, dx, y, x int) (int, int, int, int) {
+		// Rotate if we cannot move to the next position
+		if (y+dy < 0 || y+dy >= m) || (x+dx < 0 || x+dx >= n) || matrix[y+dy][x+dx] != UNSET {
+			// (0, 1) -> (1, 0) -> (0, -1) -> (-1, 0) -> (0, 1)
+			dy, dx = dx, -dy
+		}
+
+		y += dy
+		x += dx
+
+		return dy, dx, y, x
+	}
+
+	y, x := 0, 0
+	dy, dx := 0, 1
+	for node != nil {
+		matrix[y][x] = node.Val
+
+		dy, dx, y, x = Next(dy, dx, y, x)
+		node = node.Next
+	}
+
+	return matrix
+}