poj 2676 sudoku

#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;

int Graph[10][10];
bool InputRow[10][10];
bool InputCol[10][10];
bool Grid[10][10];

bool DFS(int x, int y)
{
if(x == 9)
return true;
if(Graph[x][y])
{
if(y == 8)
{
if(DFS(x+1, 0))
return true;
return false;
}
if(DFS(x, y+1))
return true;
return false;
}

for(int i = 1; i <= 9; ++i)
{
int k = 3 * (x/3) + (y/3);
if(!InputRow[x][i] && !InputCol[y][i] && !Grid[k][i])
{
Graph[x][y] = i;
InputRow[x][i] = true;
InputCol[y][i] = true;
Grid[k][i] = true;

if(y == 8)
{
if(DFS(x+1, 0))
return true;
}
if(DFS(x, y+1))
return true;

Graph[x][y] = 0;
InputRow[x][i] = false;
InputCol[y][i] = false;
Grid[k][i] = false;
}
}
return false;
}

int main()
{
char M[10][10];
int T, i, j;
scanf("%d", &T);
while(T--)
{
memset(InputRow, false, sizeof(InputRow));
memset(InputCol, false, sizeof(InputCol));
memset(Grid, false, sizeof(Grid));
for(i = 0; i < 9; ++i)
{
scanf("%s", M[i]);
for(j = 0; j < 9; ++j)
{
Graph[i][j] = M[i][j] - '0';
if(Graph[i][j])
{
int k = 3 * (i/3) + (j/3);
InputRow[i][Graph[i][j]] = true;
InputCol[j][Graph[i][j]] = true;
Grid[k][Graph[i][j]] = true;
}
}
}

DFS(0, 0);

for(i = 0; i < 9; ++i)
{
for(j = 0; j < 8; ++j)
printf("%d", Graph[i][j]);
printf("%d\n", Graph[i][j]);
}
}
return 0;
}