这注释是我写的么？忘记了.......

/* source:  zju 1008 */
/* describe: dfs   */
/* status:  6.83s-_- */
/* author:  sqc2936  */

#include <stdio.h>

int g=0;         //Game index
int n=0;         //Puzzle size
int q=0;         //How many different types of squares
int square[25][4];   //Source squares
int count[25];      //Quantity of a certain type of squares
int table[25];      //Solution

int place(int pos)
{
   int i;

   if(pos==n*n)
      return 1;

   for(i=0; i<q; i++)
   {
      if(count[i]==0)
         continue;

      if(pos%n!=0)
         if(square[table[pos-1]][1]!=square[i][3])
            continue;

      if(pos/n!=0)
         if(square[table[pos-n]][2]!=square[i][0])
            continue;

      table[pos]=i;

      count[i]--;

      if(place(pos+1)==1)
         return 1;

      count[i]++;
   }

   return 0;
}

int main()
{
   int i, j;
   int t, r, b, l;   //Temporary variables for input (top, right, bottom, left)

   g=0;
   q=0;

   while(1)
   {
      g++;

      scanf("%d", &n);

      if(n==0)
         break;

      q=0;

      for(i=0; i<n*n; i++)
      {
         scanf("%d %d %d %d", &t, &r, &b, &l);

         j=0;

         while(j<q)
         {
            if(square[j][0]==t && square[j][1]==r && square[j][2]==b && square[j][3]==l)
            {
               count[j]++;
               break;
            }

            j++;
         }

         if(j==q)
         {
            square[j][0]=t;
            square[j][1]=r;
            square[j][2]=b;
            square[j][3]=l;

            count[j]=1;

            q++;
         }
      }

      if(g>1)
         printf("\n");
      if(place(0)==1)
         printf("Game %d: Possible\n", g);
      else
         printf("Game %d: Impossible\n", g);
   }

   return 0;
}

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