Add 37_Sudoku_Solver.java

Author: Sean Prashad

Backtracking/37_Sudoku_Solver.java

@@ -0,0 +1,45 @@
+class Solution {
+ public void solveSudoku(char[][] board) {
+ if (board == null || board.length == 0) {
+ return;
+ }
+
+ solve(board);
+ }
+
+ private boolean isValid(char[][] board, int row, int col, char num) {
+ int blockRow = (row / 3) * 3, blockCol = (col / 3) * 3;
+
+ for (int i = 0; i < 9; i++) {
+ if (board[i][col] == num || board[row][i] == num || board[blockRow + i / 3][blockCol + i % 3] == num) {
+ return false;
+ }
+ }
+
+ return true;
+ }
+
+ private boolean solve(char[][] board) {
+ for (int i = 0; i < board.length; i++) {
+ for (int j = 0; j < board[i].length; j++) {
+ if (board[i][j] == '.') {
+ for (char c = '1'; c <= '9'; c++) {
+ if (isValid(board, i, j, c)) {
+ board[i][j] = c;
+
+ if (solve(board)) {
+ return true;
+ } else {
+ board[i][j] = '.';
+ }
+ }
+ }
+
+ return false;
+ }
+ }
+ }
+
+ return true;
+ }
+}