回溯——数独问题

代码

public class Sudoku{
    public static void main(String[] args){
        int[][] board=new int[9][9];
        Scanner scanner = new Scanner(System.in);
        for(int i=0;i<board.length;i++){
            String line = scanner.nextLine();
            for(int j=0;j<board.length;j++){
                board[i][j]=Integer.parseInt(line.charAt(j)+"");//把输入的字分开
                
            }
        }
        solve(0,0,board);
    }
    private static void solve(int row,int col,int[][] board){
        if(row==9){
            print(board);
            return;
        }else{
            if(board[row][col]==0){
                for(int num=1;num<=9;num++){
                    if(!isExist(row,col,num,board)){
                        board[row][col]=num;
                        solve(row+(col+1)/9,(col+1)%9,board);
                    }
                    board[row][col]=0;
                }
            }else{
                solve(row+(col+1)/9,(col+1)%9,board);
            }
        }
    }
    
     public static void print(int[][] board){
        for(int i=0;i<board.length;i++){
            for(int j=0;j<board.length;j++){
                System.out.print(board[i][j]+" ");
            }
             System.out.println();
        }
    }
    
    //判断
    private static boolean isExist(int row,int col,int num,int[][] boread){
        //同行
        for(int c=0;c<9;c++){
            if(board[row][c]==num){
                return true;
            }
        }
        
        //同列
        for(int r=0;r<9;r++){
            if(board[r][col]==num){
                return true;
            }
        }
        //3*3
        int rowMin = 0;
        int rowMax = 0;
        int colMin = 0;
        int colMax = 0;
        //约束行
        if(row>=0&&row<=2){
            rowMin=0;
            rowMax=2;
        }
        if(row>=3&&row<=5){
            rowMin=3;
            rowMax=5;
        }
        if(row>=6&&row<=8){
            rowMin=6;
            rowMax=8;
        }
        //约束列
        if(col>=0&&col<=2){
            colMin=0;
            colMax=2;
        }
         if(col>=3&&col<=5){
            colMin=3;
            colMax=5;
        }
         if(col>=6&&col<=8){
            colMin=6;
            colMax=8;
        }
        
        for(int r=rowMin;r<=rowMax;r++){//行遍历
            for(int c=colMin;c<=colMax;c++){//列遍历
                if(board[r][c]==num){
                    return true;
                } 
            }
        }
         return false;
    }
    
}