USACO sec2.1 Hamming Codes

/*
PROG : hamming
LANG : C++
*/
# include <stdio.h>

# define id(x) ((x)>>3)
# define of(x) ((x)&0x7)
# define get(x) ((h[id(x)]>>of(x))&0x1)
# define set(x) (h[id(x)] |= (0x1<<of(x)))

int n, b, d;
char h[(1<<5) + 1];
int sol[70];
/*************************************************/
int dis(int x, int y)
{
int s = x ^ y, r = 0;
while (s)
{
++r;
s &= s-1;
}
return r;
}

void search(int cur, int cnt)
{
int i, j;
if (cnt > n) return ;
for (i = cur+1; i < (1<<b); ++i) if (!get(i))
{
for (j = 1; j <= cnt; ++j)
if (dis(sol[j], i) < d) break;
set(i);
if (j > cnt) {sol[cnt+1] = i; search(i, cnt+1);}
}
}
/*************************************************/
void solve(void)
{
int i;
scanf("%d%d%d", &n, &b, &d);
sol[1] = 0, set(0);
search(0, 1);
for (i = 1; i <= n; ++i)
{
if (i%10 != 1) putchar(' ');
printf("%d", sol[i]);
if (i<n && i%10 == 0) putchar('\n');
}
putchar('\n');
}

int main()
{
freopen("hamming.in", "r", stdin);
freopen("hamming.out", "w", stdout);

solve();

fclose(stdin);
fclose(stdout);

return 0;
}