added valid Sudoku solution using Set()

Author: DevDelvo

dictionariesAndHashMaps/validSudoku.js

@@ -0,0 +1,117 @@
+// Determine if a 9x9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:
+
+// Each row must contain the digits 1-9 without repetition.
+// Each column must contain the digits 1-9 without repetition.
+// Each of the 9 3x3 sub-boxes of the grid must contain the digits 1-9 without repetition.
+
+// A partially filled sudoku which is valid.
+
+// The Sudoku board could be partially filled, where empty cells are filled with the character '.'.
+
+// Example 1:
+// Input:
+// [
+//   ["5","3",".",".","7",".",".",".","."],
+//   ["6",".",".","1","9","5",".",".","."],
+//   [".","9","8",".",".",".",".","6","."],
+//   ["8",".",".",".","6",".",".",".","3"],
+//   ["4",".",".","8",".","3",".",".","1"],
+//   ["7",".",".",".","2",".",".",".","6"],
+//   [".","6",".",".",".",".","2","8","."],
+//   [".",".",".","4","1","9",".",".","5"],
+//   [".",".",".",".","8",".",".","7","9"]
+// ]
+// Output: true
+// Example 2:
+// Input:
+// [
+//   ["8","3",".",".","7",".",".",".","."],
+//   ["6",".",".","1","9","5",".",".","."],
+//   [".","9","8",".",".",".",".","6","."],
+//   ["8",".",".",".","6",".",".",".","3"],
+//   ["4",".",".","8",".","3",".",".","1"],
+//   ["7",".",".",".","2",".",".",".","6"],
+//   [".","6",".",".",".",".","2","8","."],
+//   [".",".",".","4","1","9",".",".","5"],
+//   [".",".",".",".","8",".",".","7","9"]
+// ]
+// Output: false
+
+// Explanation: Same as Example 1, except with the 5 in the top left corner being
+//     modified to 8. Since there are two 8's in the top left 3x3 sub-box, it is invalid.
+// Note:
+
+// A Sudoku board (partially filled) could be valid but is not necessarily solvable.
+// Only the filled cells need to be validated according to the mentioned rules.
+// The given board contain only digits 1-9 and the character '.'.
+// The given board size is always 9x9.
+
+function isValidSudoku(board) {
+  const isValid = validator();
+
+  for (let i = 0; i < 9; i++) {
+    for (let j = 0; j < 9; j++) {
+      if (!isValid(i, j, board[i][j])) {
+        return false;
+      }
+    }
+  }
+  return true;
+}
+
+const validator = () => {
+  const horizontal = Array.from(Array(9), () => new Set());
+  const vertical = Array.from(Array(9), () => new Set());
+  const boxes = Array.from(Array(9), () => new Set());
+
+  return (row, col, value) => {
+    if (value === '.') {
+      return true;
+    }
+
+    if (horizontal[row].has(value)) {
+      return false;
+    }
+
+    if (vertical[col].has(value)) {
+      return false;
+    }
+
+    const box = Math.floor(row / 3) * 3 + Math.floor(col / 3);
+    if (boxes[box].has(value)) {
+      return false;
+    }
+
+    horizontal[row].add(value);
+    vertical[col].add(value);
+    boxes[box].add(value);
+    return true;
+  }
+}
+
+const board1 = [
+  ["5", "3", ".", ".", "7", ".", ".", ".", "."],
+  ["6", ".", ".", "1", "9", "5", ".", ".", "."],
+  [".", "9", "8", ".", ".", ".", ".", "6", "."],
+  ["8", ".", ".", ".", "6", ".", ".", ".", "3"],
+  ["4", ".", ".", "8", ".", "3", ".", ".", "1"],
+  ["7", ".", ".", ".", "2", ".", ".", ".", "6"],
+  [".", "6", ".", ".", ".", ".", "2", "8", "."],
+  [".", ".", ".", "4", "1", "9", ".", ".", "5"],
+  [".", ".", ".", ".", "8", ".", ".", "7", "9"]
+]
+
+const board2 = [
+  ["8", "3", ".", ".", "7", ".", ".", ".", "."],
+  ["6", ".", ".", "1", "9", "5", ".", ".", "."],
+  [".", "9", "8", ".", ".", ".", ".", "6", "."],
+  ["8", ".", ".", ".", "6", ".", ".", ".", "3"],
+  ["4", ".", ".", "8", ".", "3", ".", ".", "1"],
+  ["7", ".", ".", ".", "2", ".", ".", ".", "6"],
+  [".", "6", ".", ".", ".", ".", "2", "8", "."],
+  [".", ".", ".", "4", "1", "9", ".", ".", "5"],
+  [".", ".", ".", ".", "8", ".", ".", "7", "9"]
+]
+
+console.log(isValidSudoku(board1)); // true
+console.log(isValidSudoku(board2)); // false