Floyd_Warshall POJ 3660 Cow Contest

#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;

const int N = 1e2 + 5;
bool d

;
int in
;
int n, m;

void Floyd_Warshall(void)	{
for (int k=1; k<=n; ++k)	{
for (int i=1; i<=n; ++i)	{
for (int j=1; j<=n; ++j)	{
d[i][j] = (d[i][j] || (d[i][k] && d[k][j]));
}
}
}
}

int main(void)	{
while (scanf ("%d%d", &n, &m) == 2)	{
memset (d, false, sizeof (d));
memset (in, 0, sizeof (in));
for (int u, v, i=1; i<=m; ++i)	{
scanf ("%d%d", &u, &v);
d[u][v] = true;
in[v]++;
}
Floyd_Warshall ();
int ans = 0;
for (int i=1; i<=n; ++i)	{
int c1 = 0, c2 = 0;
for (int j=1; j<=n; ++j)	{
if (i == j)	continue;
if (d[i][j])	c1++;
if (d[j][i])	c2++;
}
if (c1 + c2 == n - 1)	ans++;
}
printf ("%d\n", ans);
}

return 0;
}