SudokuSolver.java

Change-Id: Iaf6e0b59a929f642abd17747f49e458545f908ac

Author: applewjg

SudokuSolver.java

@@ -0,0 +1,47 @@
+/*
+ Author:     King, [email protected]
+ Date:       Dec 20, 2014
+ Problem:    Sudoku Solver
+ Difficulty: Medium
+ Source:     https://oj.leetcode.com/problems/sudoku-solver/
+ Notes:
+ Write a program to solve a Sudoku puzzle by filling the empty cells.
+ Empty cells are indicated by the character '.'.
+ You may assume that there will be only one unique solution.
+
+ Solution: back-tracking..
+ */
+public class Solution {
+    public void solveSudoku(char[][] board) {
+        solve(board);
+    }
+    boolean solve(char[][] board){
+        for(int i = 0;i<9;i++){
+            for(int j=0;j<9;j++){
+                if(board[i][j]=='.'){
+                    for(char ch = '1';ch<='9';ch++){
+                        board[i][j]=ch;
+                        if(isValidSudoKu(board,i,j)&&solve(board)) return true;
+                        board[i][j]='.';
+                    }
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+    boolean isValidSudoKu(char[][] board, int x, int y){
+        for(int i = 0; i<9; i++){
+            if(i!=y&&board[x][i]==board[x][y]) return false;
+        }
+        for(int i=0;i<9;i++){
+            if(i!=x&&board[i][y]==board[x][y]) return false;
+        }
+        for(int i=3*(x/3);i<3*(x/3)+3;i++){
+            for(int j=3*(y/3);j<3*(y/3)+3;j++){
+                if(i!=x&&j!=y&&board[i][j]==board[x][y]) return false;
+            }
+        }
+        return true;
+    }
+}