Add solution #36

Author: JoshCrozier

solutions/0036-valid-sudoku.js

@@ -0,0 +1,38 @@
+/**
+ * 36. Valid Sudoku
+ * https://leetcode.com/problems/valid-sudoku/
+ * Difficulty: Medium
+ *
+ * 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.
+ *
+ * The Sudoku board could be partially filled, where empty cells are filled with the character '.'.
+ */
+
+/**
+ * @param {character[][]} board
+ * @return {boolean}
+ */
+var isValidSudoku = function(board) {
+  const rows = new Array(9).fill().map(() => new Set());
+  const columns = new Array(9).fill().map(() => new Set());
+  const boxes = new Array(9).fill().map(() => new Set());
+
+  for (let i = 0; i < 9; i++) {
+    for (let j = 0; j < 9; j++) {
+      const value = board[i][j];
+      const k = Math.floor(i / 3) * 3 + Math.floor(j / 3);
+      const options = [rows[i], columns[j], boxes[k]];
+
+      if (options.some(option => option.has(value))) return false;
+      if (value === '.') continue;
+      options.forEach(option => option.add(value));
+    }
+  }
+
+  return true;
+};