HDU 5965 Gym Class 贪心+toposort

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <string>
#include <stack>
#include <vector>
#include <map>
#include <queue>
#include <algorithm>
#include <utility>
using namespace std;
typedef long long LL;
const int N=1e5+5;
const int INF=0x3f3f3f3f;
const LL mod=1e9+7;
priority_queue<int>q;
struct Edge{
int v,next;
}edge
;
int head
,tot;
void add(int u,int v){
edge[tot].v=v;
edge[tot].next=head[u];
head[u]=tot++;
}
int d
;
int main()
{
int T,cas=0;
scanf("%d",&T);
while(T--){
// printf("Case #%d:\n",++cas);
int n,m;
scanf("%d%d",&n,&m);
memset(head,-1,sizeof(head)),tot=0;
memset(d,0,sizeof(d));
for(int i=1;i<=m;i++){
int u,v;
scanf("%d%d",&u,&v);
add(u,v);++d[v];
}
while(!q.empty())q.pop();
for(int i=1;i<=n;++i)
if(!d[i])q.push(i);
LL ans=0;int cur=-1;
while(!q.empty()){
int u=q.top();
q.pop();
if(cur==-1)cur=u;
else cur=min(cur,u);
ans+=cur;
for(int i=head[u];~i;i=edge[i].next){
int v=edge[i].v;
--d[v];
if(!d[v])q.push(v);
}
}
printf("%I64d\n",ans);
}
return 0;
}