poj 2676 Sudoku

#include<stdio.h>
#include<string.h>
#include<iostream>
#include<algorithm>
using namespace std;

int mp[10][10],row[10][10],col[10][10],grid[10][10];

int get(int x,int y)
{
    if(x>=1&&x<=3)
    {
        if(y>=1&&y<=3) return 1;
        else if(y>=4&&y<=6) return 4;
        else return 7;
    }
    else if(4<=x&&x<=6)
    {
        if(y>=1&&y<=3) return 2;
        else if(y>=4&&y<=6) return 5;
        else return 8;
    }
    else
    {
        if(y>=1&&y<=3) return 3;
        else if(y>=4&&y<=6) return 6;
        else return 9;
    }
}

int dfs(int x,int y)
{
    if(x==10) return 1;
    int flag=0,i;
    if(mp[x][y])
    {
        if(y==9)
            flag=dfs(x+1,1);
        else
            flag=dfs(x,y+1);

        if(flag) return 1;
        else return 0;
    }
    else
    {
        for(i=1; i<=9; i++)
        {
            int k=get(x,y);
            if(!row[x][i]&&!col[y][i]&&!grid[k][i])
            {
                row[x][i]=1;
                col[y][i]=1;
                grid[k][i]=1;
                mp[x][y]=i;
                if(y==9)
                    flag=dfs(x+1,1);
                else
                    flag=dfs(x,y+1);

                if(flag==0)
                {
                    row[x][i]=0;
                    col[y][i]=0;
                    grid[k][i]=0;
                    mp[x][y]=0;
                }
                else
                    return 1;
            }
        }
    }
    return 0;
}

int main()
{
    int i,j,k,_;
    char s;
    scanf("%d",&_);
    while(_--)
    {
        memset(row,0,sizeof(row));
        memset(col,0,sizeof(col));
        memset(grid,0,sizeof(grid));

        for(i=1; i<=9; i++)
            for(j=1; j<=9; j++)
            {
                cin>>s;
                mp[i][j]=s-'0';
                if(mp[i][j])
                {
                    k=get(i,j);
                    row[i][mp[i][j]]=1;
                    col[j][mp[i][j]]=1;
                    grid[k][mp[i][j]]=1;
                }
            }
        dfs(1,1);

        for(i=1; i<=9; i++)
        {
            for(j=1; j<=9; j++)
            {
                printf("%d",mp[i][j]);
            }
            printf("\n");
        }
    }
    return 0;
}