Create 37-sudoku-solver.js

Author: everthis

37-sudoku-solver.js

@@ -0,0 +1,36 @@
+/**
+ * @param {character[][]} board
+ * @return {void} Do not return anything, modify board in-place instead.
+ */
+const solveSudoku = function(board) {
+  dfs(0, 0)
+  function dfs(row, col) {
+    if (row === 9) return true
+    if (col === 9) return dfs(row + 1, 0)
+    if (board[row][col] === ".") {
+      for (let num = 1; num <= 9; num++) {
+        if (isValid(row, col, `${num}`)) {
+          board[row][col] = `${num}`
+          if (dfs(row, col + 1)) return true
+          board[row][col] = "."
+        }
+      }
+    } else {
+      return dfs(row, col + 1)
+    }
+    return false
+  }
+  function isValid(row, col, num) {
+    for (let rowIdx = 0; rowIdx < 9; rowIdx++) if (board[rowIdx][col] === num) return false
+    for (let colIdx = 0; colIdx < 9; colIdx++) if (board[row][colIdx] === num) return false
+
+    let squareRowStart = row - (row % 3)
+    let squareColStart = col - (col % 3)
+    for (let rIdx = 0; rIdx < 3; rIdx++) {
+      for (let cIdx = 0; cIdx < 3; cIdx++) {
+        if (board[squareRowStart + rIdx][squareColStart + cIdx] === num) return false
+      }
+    }
+    return true
+  }
+}