HDU 1285 确定比赛名次 （拓扑排序）

#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdlib>
#include <sstream>
#include <cstdio>
#include <vector>
#include <cmath>
#include <queue>
#include <stack>
#include <set>
#include <map>
#define lson o<<1, l, m
#define rson o<<1|1, m+1, r
#define PII pair<int, int>
#define ALL(x) x.begin(),x.end()
#define mem(a) memset(a,0,sizeof(a))
typedef long long ll;
const double pi = acos(-1.0);
const int MAX = 0x3f3f3f3f;
const ll mod = 1000000007ll;
const int N = 250005;
using namespace std;

struct C {
int ne, to;
} e
;
int n, m;
int du[505], he[505];

void add(int id, int x, int y) {
e[id].to = y;
e[id].ne = he[x];
he[x] = id;
}

int main() {

//    freopen("in.txt", "r", stdin);
//    freopen("out.txt", "w", stdout);

while(cin >> n >> m) {
mem(du);
memset(he, -1, sizeof(he));
for(int i = 1; i <= m; i++) {
int x, y;
scanf("%d%d", &x, &y);
du[y]++;
add(i, x, y);
}
int cnt = 0;
while(1) {
for(int i = 1; i <= n; i++) if(du[i] == 0) {
printf("%d", i);
cnt++;
if(cnt < n) printf(" ");
else {
puts("");
break;
}
du[i]--;
for(int j = he[i]; j != -1; j = e[j].ne) {
du[ e[j].to ]--;
}
break;
}
if(cnt == n) break;
}

}

return 0;

}