I really stuck with this, I don't know how to make my algorithm faster

here is my code:
#include <stdio.h>
char board[10][10];
char letter[66],num[66];
int n,s=0,ncuad;
int pos_f[8]={-1,-2,-2,-1, 1, 2, 2, 1};
int pos_c[8]={-2, 1,-1, 2, 2, 1,-1,-2};

init_board(){
    int i,j;
    for(i=1;i<=n;i++)
        for(j=1;j<=n;j++)
            board[i][j]='0';
}

search(int i,int f,int c){
    int j=0;
    if(s==1)
        return 0;
  if(board[f][c]=='0'){
     board[f][c]='1';
     switch(f){
           case 1: letter[i]='a';break;
        case 2: letter[i]='b';break;
        case 3: letter[i]='c';break;
        case 4: letter[i]='d';break;
               case 5: letter[i]='e';break;
               case 6: letter[i]='f';break;
               case 7: letter[i]='g';break;
               case 8: letter[i]='h';break;
     }
     num[i]=c;
     if(i==ncuad)
              s=1;
       while(j<8 && s==0){
           if((f+pos_f[j])>0 && (f+pos_f[j])<=n)
         if((c+pos_c[j])>0 && (c+pos_c[j])<=n)
               search(i+1,f+pos_f[j],c+pos_c[j]);
       j++;
     }
         board[f][c]='0';
   }
}

int main(){
    int i,j;
  scanf("%d",&n);
  ncuad=n*n;
  init_board();
     for(i=1;i<=n;i++)
         for(j=1;j<=n;j++)
           search(1,i,j);
    if(s){
       for(i=1;i<=ncuad;i++)
         printf("%c%d ",letter[i],num[i]);
         return 0;
    }
    else
     printf("IMPOSSIBLE\n");
  return 0;
}

if someone can help me I would appreciate a lot!!

else
   begin
   writeln('a1');
   writeln('b3');
   writeln('a5');
   writeln('b7');
   writeln('d8');
   writeln('c6');
   writeln('b4');
   writeln('a2');
   writeln('c3');
   writeln('b1');
   writeln('a3');
   writeln('b5');
   writeln('a7');
   writeln('c8');
   writeln('b6');
   writeln('a4');
   writeln('c5');
   writeln('a6');
   writeln('b8');
   writeln('d7');
   writeln('f8');
   writeln('e6');
   writeln('d4');
   writeln('c2');
   writeln('e3');
   writeln('d1');
   writeln('b2');
   writeln('c4');
   writeln('d6');
   writeln('e8');
   writeln('g7');
   writeln('f5');
   writeln('e7');
   writeln('g8');
   writeln('f6');
   writeln('h7');
   writeln('g5');
   writeln('e4');
   writeln('d2');
   writeln('f1');
   writeln('h2');
   writeln('f3');
   writeln('e1');
   writeln('g2');
   writeln('h4');
   writeln('g6');
   writeln('h8');
   writeln('f7');
   writeln('h6');
   writeln('g4');
   writeln('e5');
   writeln('d3');
   writeln('c1');
   writeln('e2');
   writeln('g1');
   writeln('h3');
   writeln('f2');
   writeln('h1');
   writeln('g3');
   writeln('h5');
   writeln('f4');
   writeln('d5');
   writeln('c7');
   writeln('a8');
   end;

thanks!
but can I ask you two questions...?
first, how many time takes in your computer if you run my code to get the solution for n=8? because my computer is veryy slow and get stuck
and number two
is it any way to solve it the problem without precalc?? (sorry for my bad english)
and thanks again!!! :D:D:D:D:)
byee! and good luck!

I didn't use precalc.
I calculated answer for N using answer for N-1
if it was not 'No Solution' I took first N moves from it.

Use the priority array for the chessboard :

void init()
{
    int a,b,c;
int chessboard[8][8]={0};
int direction[8][2]=
{
    {2,1},{-2,1},{2,-1},{-2,-1},
    {1,2},{-1,2},{1,-2},{-1,-2},
};
    for(a=0;a<n;a++)
    {
        for(b=0;b<n;b++)
        {
            int count=0;
            for(c=0;c<n;c++)
            {
                int x1 = a+direction[c][0];
                int y1 = b+direction[c][1];
                if(x1>=0&&x1<n&&y1>=0&&y1<n) count++;
            }
            chessboard[a][b] = count;
        }
    }
}

For example, n = 8 :

2 3 4 4 4 4 3 2
3 4 6 6 6 6 4 3
4 6 8 8 8 8 6 4
4 6 8 8 8 8 6 4
4 6 8 8 8 8 6 4
4 6 8 8 8 8 6 4
3 4 6 6 6 6 4 3
2 3 4 4 4 4 3 2

go to the cell with minimum priority first !
Good luck !

Edited by author 17.02.2009 12:04

Edited by author 17.02.2009 12:04

How can here be >=10 tests if 1<=n<=8?

Great tip, thank you!