Sudoku Solver

#include <stdio.h>

int row[9],col[9],box[3][3];
int g[9][9];
bool test(int & x,int j) { return (x & (1<<j)) >0 ;}
void set(int & x,int j) { x |= (1<<j) ;}
void unset(int & x,int j) { x &= (~(1<<j)); }
bool doit(int x,int y)
{
 if(x==9) return true;
 if(g[x][y]) return doit(x+(y==8),(y+1)%9);
 for(int i=0; i<9; i++) {
  if(!test(row[x],i) && !test(col[y],i) && !test(box[x/3][y/3],i)){
   set(row[x],i);
   set(col[y],i);
   set(box[x/3][y/3],i);
   if(doit(x+(y==8),(y+1)%9)) {
    g[x][y] = i+1;
    return true;
   }
   unset(row[x],i); unset(col[y],i); unset(box[x/3][y/3],i);
  }
 }
 return false;
}
main()
{
 for(int i=0; i<9; i++) {
  for(int j=0; j<9; j++){
   int k;
   scanf("%d",&k);
   if(k--){
    g[i][j] = k+1;
    row[i] |= (1<<k);
    col[j] |= (1<<k);
    box[i/3][j/3] |= (1<<k);
   }
  }
 }
 if(doit(0,0)){
  for(int i=0; i<9; i++) {
   for(int j=0; j<9; j++) 
    printf("%d%s", g[i][j], (j==8?"\n":(j%3==2?" | ":" ")));
   if(i != 8 && i%3==2){
    printf("---------------------\n");;
   }
  }
 }
 else{
  printf("No Solution!\n");
 }
}

Thanks to Lakshmi Subrahmanyam for providing the solution.