37. Sudoku Solver (java)

Author: bluesword12350

solution/0037.Sudoku Solver/Solution.java

@@ -0,0 +1,51 @@
+class Solution {
+    private char[][] board;
+    private boolean[][] rows;
+    private boolean[][] cols;
+    private boolean[][] subBox;
+
+    public void solveSudoku(char[][] board) {
+        this.board = board;
+        this.rows = new boolean[9][9];
+        this.cols = new boolean[9][9];
+        this.subBox = new boolean[9][9];
+        int val;
+        for (int i = 0; i < 9; i++) {
+            for (int j = 0; j < 9; j++) {
+                if (board[i][j] != '.') {
+                    val = board[i][j] - '0';
+                    rows[i][val - 1] = true;
+                    cols[j][val - 1] = true;
+                    subBox[(i / 3) * 3 + j / 3][val - 1] = true;
+                }
+            }
+        }
+        fillSudoku(0, 0);
+    }
+
+    private boolean fillSudoku(int i, int j) {
+        if (i == 9) return true;
+        int x = i, y = j;
+        if (y == 8) {
+            x++;
+            y = 0;
+        } else y++;
+        if (board[i][j] == '.') {
+            for (int k = 1; k <= 9; k++) {
+                if (!rows[i][k - 1] && !cols[j][k - 1] && !subBox[(i / 3) * 3 + j / 3][k - 1]) {
+                    rows[i][k - 1] = true;
+                    cols[j][k - 1] = true;
+                    subBox[(i / 3) * 3 + j / 3][k - 1] = true;
+                    if (fillSudoku(x, y)) {
+                        board[i][j] = (char) (k + '0');
+                        return true;
+                    }
+                    rows[i][k - 1] = false;
+                    cols[j][k - 1] = false;
+                    subBox[(i / 3) * 3 + j / 3][k - 1] = false;
+                }
+            }
+            return false;
+        } else return fillSudoku(x, y);
+    }
+}