pacific atlantic water flow solution

Author: yhkee0404

pacific-atlantic-water-flow/yhkee0404.scala

@@ -0,0 +1,37 @@
+object Solution {
+    val _DRCS = Array(
+        Array(-1, 0),
+        Array(0, -1),
+        Array(0, 1),
+        Array(1, 0),
+    )
+    def pacificAtlantic(heights: Array[Array[Int]]): List[List[Int]] = {
+        val visited = Array.fill[Array[Int]](heights.length)(
+            Array.fill[Int](heights.head.length)(0)
+        )
+        for (i <- heights.indices) {
+            dfs(heights, visited, i, 0, 1)
+            dfs(heights, visited, i, heights.head.length - 1, 2)
+        }
+        for (i <- heights.head.indices) {
+            dfs(heights, visited, 0, i, 1)
+            dfs(heights, visited, heights.length - 1, i, 2)
+        }
+        (
+            for {
+                r <- visited.indices
+                c <- visited.head.indices
+                if visited(r)(c) == 3
+            } yield List(r, c)
+        ).toList
+    }
+    def dfs(heights: Array[Array[Int]], visited: Array[Array[Int]], r: Int, c: Int, v: Int): Unit = {
+        visited(r)(c) |= v
+        _DRCS.map { case Array(dr, dc) => (r + dr, c + dc) }
+                .filter { case (nr, nc) => nr != -1 && nr != heights.length && nc != -1 && nc != heights.head.length }
+                .filter { case (nr, nc) => (visited(nr)(nc) & v) == 0 && heights(r)(c) <= heights(nr)(nc) }
+                .foreach { case (nr, nc) =>
+                    dfs(heights, visited, nr, nc, v)
+                }
+    }
+}