[不会]luogu_P1954_航空管制（拓扑排序

和P3243有相似的地方，但是不懂

#include<bits/stdc++.h>
#define R register
using namespace std;
const int maxn=2009;
inline int read(){
    R int ret=0,fix=1;R char ch;
    while(!isdigit(ch=getchar()))fix=ch=='-'?-1:fix;
    do ret=(ret<<1)+(ret<<3)+ch-'0';
    while(isdigit(ch=getchar()));
    return fix*ret;
}
int n,m;
struct noe{
    int v,nxt;
}e[10009];
int head[maxn],cnt;
inline void add(int u,int v){
    e[++cnt].v=v;e[cnt].nxt=head[u];head[u]=cnt;
}
int k[maxn],in[maxn],tmp[maxn];
struct node{
    int x,d;
    node(){}
    node(int xx,int dd){x=xx;d=dd;}
    bool operator <(const node&t)const{
        return d<t.d;
    }
};
priority_queue<node>q;
inline int work(int x){
    memcpy(in,tmp,sizeof(in));
    in[x]=n;//忽略要求的飞机 
    while(!q.empty())q.pop();
    for(R int i=1;i<=n;i++)if(!in[i])q.push(node(i,k[i]));
    for(R int i=n;i>=1;i--){
        if(q.empty()||q.top().d<i)return i;//没有飞机可起飞了 
        int x=q.top().x;q.pop();
        for(R int i=head[x];i;i=e[i].nxt){
            if(!--in[e[i].v])q.push(node(e[i].v,k[e[i].v]));
        }
    }
}
int ans[maxn],ccc;
int main(){
//    freopen("testdata (7).in","r",stdin);
//    freopen("test.out","w",stdout);
    scanf("%d%d",&n,&m);
    for(R int i=1;i<=n;i++)k[i]=read();
    for(R int i=1,u,v;i<=m;i++){
        u=read();v=read();
        add(v,u);in[u]++;
    }
    memcpy(tmp,in,sizeof(in));
    for(R int i=1;i<=n;i++)if(!in[i])q.push(node(i,k[i]));
    while(!q.empty()){
        int x=q.top().x;q.pop();ans[++ccc]=x;
        for(R int i=head[x];i;i=e[i].nxt){
            if(!--in[e[i].v])q.push(node(e[i].v,k[e[i].v]));
        }
    }
    for(R int i=ccc;i>=1;i--)printf("%d ",ans[i]);puts("");
    for(R int i=1;i<=n;i++)printf("%d ",work(i));
    
}