Sudoku Solver

 

Total Accepted: 13937 

Total Submissions: 66832

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.

A sudoku puzzle...

...and its solution numbers marked in red.

public class Solution {    public void solveSudoku(char[][] board) {           solve(board);           }    private boolean solve(char[][] board) {         for (int i = 0; i < 9; i++) {            for (int j = 0; j < 9; j ++) {                if (board[i][j] =='.') {                    for (char k = '1'; k <= '9'; k++) {                        board[i][j] = k;                        if (isValid(board, i, j) && solve(board)) {                            return true;                        }                        board[i][j] = '.';                    }                    return false;                }            }        }        return true;    }    private boolean isValid(char[][] board,int x, int y ) {        boolean [][] square = new boolean[9][9];        for (int i = 0; i < 9; i++) {            if (y != i &&board[x][y] == board[x][i]){                return false;            }        }        for (int i = 0; i < 9; i++) {            if (x != i &&board[i][y] == board[x][y]){                return false;            }        }        for (int i = (x / 3) * 3; i < (x / 3) * 3 + 3; i++) {            for (int j = (y /3) * 3; j < (y / 3) *3 + 3; j++) {                if (x != i && y != j && board[i][j] == board[x][y]) {                    return false;                }            }        }        return true;    }    }

这个题目比較有意图。第一次做的时候　是对每个位置生成后的做推断。在ECLIPSE上是过的。可是在ＯＪ上超时了。

之后才想到，并不须要对整个矩阵做推断，仅仅要对更改位置的字进行推断是不是符合要求就能够了！