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;
}