[hackerrank] "DFS: Connected Cell in a Grid" 추가

Author: codehumane

src/main/kotlin/hackerrank/graphs/DFSConnectedCellInAGrid.kt

@@ -0,0 +1,54 @@
+package hackerrank.graphs
+
+import kotlin.math.max
+
+fun maxRegion(grid: Array<Array<Int>>): Int {
+
+    var result = 0
+    val visited = Array(grid.size) {
+        Array(grid.first().size) {
+            false
+        }
+    }
+
+    grid.indices.forEach { row ->
+        grid.first().indices.forEach inner@{ col ->
+            if (visited[row][col]) return@inner
+
+            val size = calculateRegion(
+                grid,
+                visited,
+                row,
+                col
+            )
+
+            result = max(result, size)
+        }
+    }
+
+    return result
+}
+
+fun calculateRegion(
+    grid: Array<Array<Int>>,
+    visited: Array<Array<Boolean>>,
+    row: Int,
+    col: Int
+): Int {
+
+    if (0 > row || row >= grid.size) return 0
+    if (0 > col || col >= grid.first().size) return 0
+    if (grid[row][col] == 0) return 0
+    if (visited[row][col]) return 0
+
+    visited[row][col] = true
+    var count = 1
+
+    (row - 1..row + 1).forEach { r ->
+        (col - 1..col + 1).forEach { c ->
+            count += calculateRegion(grid, visited, r, c)
+        }
+    }
+
+    return count
+}

src/test/kotlin/hackerrank/graphs/DFSConnectedCellInAGridKtTest.kt

@@ -0,0 +1,82 @@
+package hackerrank.graphs
+
+import org.junit.Assert.assertEquals
+import org.junit.Test
+
+class DFSConnectedCellInAGridKtTest {
+
+    @Test
+    fun `maxRegion sample test case 0`() {
+
+        // given
+        val input = arrayOf(
+            arrayOf(1, 1, 0, 0),
+            arrayOf(0, 1, 1, 0),
+            arrayOf(0, 0, 1, 0),
+            arrayOf(1, 0, 0, 0)
+        )
+
+        // when
+        val result = maxRegion(input)
+
+        // then
+        assertEquals(5, result)
+    }
+
+    @Test
+    fun `maxRegion sample test case 1`() {
+
+        // given
+        val input = arrayOf(
+            arrayOf(0, 0, 1, 1),
+            arrayOf(0, 0, 1, 0),
+            arrayOf(0, 1, 1, 0),
+            arrayOf(0, 1, 0, 0),
+            arrayOf(1, 1, 0, 0)
+        )
+
+        // when
+        val result = maxRegion(input)
+
+        // then
+        assertEquals(8, result)
+    }
+
+    @Test
+    fun `maxRegion sample test case 2`() {
+
+        // given
+        val input = arrayOf(
+            arrayOf(1, 0, 1, 1, 0),
+            arrayOf(1, 1, 0, 0, 1),
+            arrayOf(0, 1, 1, 1, 0),
+            arrayOf(0, 0, 0, 0, 1),
+            arrayOf(1, 1, 1, 0, 0)
+        )
+
+        // when
+        val result = maxRegion(input)
+
+        // then
+        assertEquals(10, result)
+    }
+
+    @Test
+    fun `maxRegion 대각선도 고려해야 한다`() {
+
+        // given
+        val input = arrayOf(
+            arrayOf(1, 1, 0, 0),
+            arrayOf(0, 1, 1, 0),
+            arrayOf(0, 0, 1, 0),
+            arrayOf(1, 0, 0, 1)
+        )
+
+        // when
+        val result = maxRegion(input)
+
+        // then
+        assertEquals(6, result)
+    }
+
+}