go: add «994. Rotting Oranges»

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

go/rotting-oranges.go

@@ -0,0 +1,79 @@
+package main
+
+import (
+	aq "github.com/emirpasic/gods/v2/queues/arrayqueue"
+)
+
+const (
+	EMPTY_CELL    int = 0
+	FRESH_ORANGE  int = 1
+	ROTTEN_ORANGE int = 2
+)
+
+type BFSEntry struct {
+	time int
+	y, x int
+}
+
+func orangesRotting(grid [][]int) int {
+	DIRECTIONS := [][]int{
+		[]int{0, 1},
+		[]int{0, -1},
+		[]int{1, 0},
+		[]int{-1, 0},
+	}
+
+	inBounds := func(y, x int) bool {
+		return y >= 0 && y < len(grid) && x >= 0 && x < len(grid[y])
+	}
+	countFresh := func() int {
+		fresh := 0
+
+		for _, row := range grid {
+			for _, orange := range row {
+				if orange == FRESH_ORANGE {
+					fresh++
+				}
+			}
+		}
+
+		return fresh
+	}
+	initializeQueue := func(q *aq.Queue[BFSEntry]) {
+		for y, row := range grid {
+			for x, orange := range row {
+				if orange != ROTTEN_ORANGE {
+					continue
+				}
+
+				q.Enqueue(BFSEntry{time: 0, y: y, x: x})
+			}
+		}
+	}
+
+	q := aq.New[BFSEntry]()
+	initializeQueue(q)
+
+	fresh, time := countFresh(), 0
+	for !q.Empty() && fresh > 0 {
+		value, _ := q.Dequeue()
+
+		for _, d := range DIRECTIONS {
+			ny, nx := value.y+d[0], value.x+d[1]
+			if !inBounds(ny, nx) || grid[ny][nx] != FRESH_ORANGE {
+				continue
+			}
+
+			grid[ny][nx] = ROTTEN_ORANGE
+			fresh--
+			q.Enqueue(BFSEntry{time: value.time + 1, y: ny, x: nx})
+			time = value.time + 1
+		}
+	}
+
+	if fresh > 0 {
+		return -1
+	}
+
+	return time
+}