Add Verify Sudoku Board

Author: marttp

kotlin/src/main/kotlin/common/hashtable/VerifySudokuBoard.kt

@@ -0,0 +1,42 @@
+package common.hashtable
+
+class VerifySudokuBoard {
+
+    fun solution(board: List<List<Int>>): Boolean {
+        // Create hash sets for each row, column, and subgrid to keep
+        // track of numbers previously seen on any given row, column, or
+        // subgrid.
+        val rowSet: List<HashSet<Int>> = List(9) {
+            hashSetOf()
+        }
+        val colSet: List<HashSet<Int>> = List(9) {
+            hashSetOf()
+        }
+        val subBoxSet: List<List<HashSet<Int>>> = List(3) {
+            List(3) {
+                hashSetOf()
+            }
+        }
+        for (r in 0 until 9) {
+            for (c in 0 until 9) {
+                val num = board[r][c]
+                if (num == 0) {
+                    continue
+                }
+                // Check if 'num' has been seen in the current row,
+                // column, or subgrid.
+                // Use Java/Kotlin HashSet add to confirm 'num' existing status in set
+                if (!rowSet[r].add(num)) {
+                    return false
+                }
+                if (!colSet[c].add(num)) {
+                    return false
+                }
+                if (!subBoxSet[r / 3][c / 3].add(num)) {
+                    return false
+                }
+            }
+        }
+        return true
+    }
+}

kotlin/src/test/kotlin/common/hashtable/VerifySudokuBoardTest.kt

@@ -0,0 +1,58 @@
+package common.hashtable
+
+import org.junit.jupiter.api.Assertions.*
+import org.junit.jupiter.api.Test
+
+class VerifySudokuBoardTest {
+
+    private val question = VerifySudokuBoard()
+
+    @Test
+    fun `Test case #1 - Expected True`() {
+        val board = listOf(
+            listOf(5, 3, 0, 0, 7, 0, 0, 0, 0),
+            listOf(6, 0, 0, 1, 9, 5, 0, 0, 0),
+            listOf(0, 9, 8, 0, 0, 0, 0, 6, 0),
+            listOf(8, 0, 0, 0, 6, 0, 0, 0, 3),
+            listOf(4, 0, 0, 8, 0, 3, 0, 0, 1),
+            listOf(7, 0, 0, 0, 2, 0, 0, 0, 6),
+            listOf(0, 6, 0, 0, 0, 0, 2, 8, 0),
+            listOf(0, 0, 0, 4, 1, 9, 0, 0, 5),
+            listOf(0, 0, 0, 0, 8, 0, 0, 7, 9)
+        )
+        assertTrue { question.solution(board) }
+    }
+
+    @Test
+    fun `Test case #2 - Expected False`() {
+        val board = listOf(
+            listOf(8, 3, 0, 0, 7, 0, 0, 0, 0),
+            listOf(6, 0, 0, 1, 9, 5, 0, 0, 0),
+            listOf(0, 9, 8, 0, 0, 0, 0, 6, 0),
+            listOf(8, 0, 0, 0, 6, 0, 0, 0, 3),
+            listOf(4, 0, 0, 8, 0, 3, 0, 0, 1),
+            listOf(7, 0, 0, 0, 2, 0, 0, 0, 6),
+            listOf(0, 6, 0, 0, 0, 0, 2, 8, 0),
+            listOf(0, 0, 0, 4, 1, 9, 0, 0, 5),
+            listOf(0, 0, 0, 0, 8, 0, 0, 7, 9)
+        )
+        assertFalse { question.solution(board) }
+    }
+
+
+    @Test
+    fun `Test case #3 - Expected False`() {
+        val board = listOf(
+            listOf(3, 0, 6, 0, 5, 8, 4, 0, 0),
+            listOf(5, 2, 0, 0, 0, 0, 0, 0, 0),
+            listOf(0, 8, 7, 0, 0, 0, 0, 3, 1),
+            listOf(1, 0, 2, 5, 0, 0, 3, 2, 0),
+            listOf(9, 0, 0, 8, 6, 3, 0, 0, 5),
+            listOf(0, 5, 0, 0, 9, 0, 6, 0, 0),
+            listOf(0, 3, 0, 0, 0, 8, 2, 5, 0),
+            listOf(0, 1, 0, 0, 0, 0, 0, 7, 4),
+            listOf(0, 0, 5, 2, 0, 6, 0, 0, 0)
+        )
+        assertFalse { question.solution(board) }
+    }
+}