AcWing342 道路与航线（最短路+DAG）

#include<cstdio>
#include<iostream>
#include<cstring>
#include<algorithm>
#include<queue>
#include<vector>
#define x first
#define y second
using namespace std;
typedef pair<int,int> pll;
const int N=1e5+10;
const int inf=0x3f3f3f3f;
vector<int> g[N];
int id[N],e[N],ne[N],w[N],h[N],idx;
bool st[N];
int t,r,p,s;
int bcnt;
int in[N];
queue<int> q;
int dis[N];
void add(int a,int b,int c){
    e[idx]=b,ne[idx]=h[a],w[idx]=c,h[a]=idx++;
}
void dfs(int x,int bcnt){
    id[x]=bcnt;
    g[bcnt].push_back(x);
    int i;
    for(i=h[x];i!=-1;i=ne[i]){
        int j=e[i];
        if(!id[j])
        dfs(j,bcnt);
    }
}
void dij(int t){
    priority_queue<pll,vector<pll>,greater<pll> > pq;
    for(auto x:g[t]){
        pq.push({dis[x],x});// all in beacause it will contribute to the next block
    }
    while(pq.size()){
        auto u=pq.top();
        pq.pop();
        int ver=u.y,distance=u.x;
        if(st[ver])
        continue;
        st[ver]=1;
        int i;
        for(i=h[ver];i!=-1;i=ne[i]){
            int j=e[i];
            if(dis[j]>dis[ver]+w[i]){
                dis[j]=dis[ver]+w[i];
                if(id[j]==id[ver]){
                    pq.push({dis[j],j});
                }
            }
            if(id[j]!=id[ver]&&--in[id[j]]==0) q.push(id[j]);
        }
    }
}
void topo(int x){
    int i;
    memset(dis,0x3f,sizeof dis);
    dis[x]=0;
    for(i=1;i<=bcnt;i++){
        if(!in[i]){
            q.push(i);
        }
    }
    while(q.size()){
        int t=q.front();
        q.pop();
        dij(t);
    }
}
int main(){
    cin>>t>>r>>p>>s;
    int i;
    memset(h,-1,sizeof h);
    for(i=1;i<=r;i++){
        int a,b,c;
        scanf("%d%d%d",&a,&b,&c);
        add(a,b,c);
        add(b,a,c);
    }
    for(i=1;i<=t;i++){
        if(!id[i]){
            bcnt++;
            dfs(i,bcnt);
        }
    }
    for(i=1;i<=p;i++){
        int a,b,c;
        scanf("%d%d%d",&a,&b,&c);
        add(a,b,c);
        in[id[b]]++;
    }
    topo(s);
    for(i=1;i<=t;i++){
        if(dis[i]>inf/2)
        cout<<"NO PATH"<<endl;
        else
        cout<<dis[i]<<endl;
    }
}