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LeetCode 37 Sudoku Solver(求解数独)

题目链接: https://leetcode.com/problems/sudoku-solver/?tab=Description
 
Problem : 解决数独问题,给出一个二维数组,将这个数独进行求解。
 
思路:
  1. 嵌套循环,三层循环体,每一行,每一列,填入从1到9的数字。判断填入之后是否合理
  2. 判断数独是否合理的函数
 
参考代码: 
 
package leetcode_50;/*** *  * @author pengfei_zheng * 求解数独问题 */public class Solution37 {    public static void solveSudoku(char[][] board) {        if(board==null ||board.length ==0)                return;        else                solve(board);    }    private static boolean solve(char[][] board) {        for(int i = 0 ; i < 9;i++){            for(int j = 0 ; j < 9;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;    }    private static boolean isValid(char[][] board, int row, int column, char c) {        for(int i = 0 ; i < 9; i ++){            if(board[row][i]==c) return false;            if(board[i][column]==c) return false;            if(board[3 * (row / 3) + i / 3][ 3 * (column / 3) + i % 3] != ‘.‘ &&                     board[3 * (row / 3) + i / 3][3 * (column / 3) + i % 3] == c) return false; //check 3*3 block        }        return true;    }    public static void main(String[]args){        long start = System.currentTimeMillis();        char[][] board={{‘8‘,‘.‘,‘.‘,‘.‘,‘.‘,‘.‘,‘.‘,‘.‘,‘.‘},                        {‘.‘,‘.‘,‘3‘,‘6‘,‘.‘,‘.‘,‘.‘,‘.‘,‘.‘},                        {‘.‘,‘7‘,‘.‘,‘.‘,‘9‘,‘.‘,‘2‘,‘.‘,‘.‘},                        {‘.‘,‘5‘,‘.‘,‘.‘,‘.‘,‘7‘,‘.‘,‘.‘,‘.‘},                        {‘.‘,‘.‘,‘.‘,‘.‘,‘4‘,‘.‘,‘7‘,‘.‘,‘.‘},                        {‘.‘,‘.‘,‘.‘,‘1‘,‘.‘,‘5‘,‘.‘,‘3‘,‘.‘},                        {‘.‘,‘.‘,‘1‘,‘.‘,‘.‘,‘.‘,‘.‘,‘6‘,‘8‘},                        {‘.‘,‘.‘,‘8‘,‘5‘,‘.‘,‘.‘,‘.‘,‘1‘,‘.‘},                        {‘.‘,‘9‘,‘.‘,‘.‘,‘.‘,‘.‘,‘4‘,‘.‘,‘.‘}                    };        solveSudoku(board);        long end = System.currentTimeMillis();        for(int i = 0 ; i < 9 ; i ++){            for(int j = 0 ; j < 9 ;j ++){                System.out.print(board[i][j]+" ");            }            System.out.println();        }        System.out.println("耗时: "+ (double)(end-start)/1000+" s");    }}

 

LeetCode 37 Sudoku Solver(求解数独)