luogu2483 【模板】k短路（[SDOI2010]魔法猪学院）

模板题

#include <iostream>
#include <cstring>
#include <cstdio>
#include <queue>
using namespace std;
int n, m, hea[5005], cnt, uu, vv, ans;
double e, ww, dis[5005];
const double eps=1e-7;
bool vis[5005];
struct Edge{
    int too, nxt;
    double val;
}edge[400005];
struct Node{
    int idx;
    double hfc, gfc;
    bool operator<(const Node &x)const{
        return hfc+gfc>x.hfc+x.gfc;
    }
}cr, cc;
queue<int> d;
priority_queue<Node> q;
void add_edge(int fro, int too, double val){
    edge[++cnt].nxt = hea[fro];
    edge[cnt].too = too;
    edge[cnt].val = val;
    hea[fro] = cnt;
}
void spfa(){
    memset(dis, 127, sizeof(dis));
    dis[n] = 0.0;
    d.push(n);
    vis[n] = true;
    while(!d.empty()){
        int x=d.front();
        d.pop();
        vis[x] = false;
        for(int i=hea[x]; i; i=edge[i].nxt)
            if(i%2==0){
                int t=edge[i].too;
                if(dis[t]>dis[x]+edge[i].val){
                    dis[t] = dis[x] + edge[i].val;
                    if(!vis[t]){
                        vis[t] = true;
                        d.push(t);
                    }
                }
            }
    }
}
void astar(){
    cr.idx = 1; cr.hfc = cr.gfc = 0.0;
    q.push(cr);
    while(!q.empty()){
        cc = q.top();
        q.pop();
        if(cc.hfc+cc.gfc-eps>e)	return ;
        if(cc.idx==n)	ans++, e -= cc.hfc;
        for(int i=hea[cc.idx]; i; i=edge[i].nxt)
            if(i%2){
                cr.idx = edge[i].too;
                cr.hfc = cc.hfc + edge[i].val;
                cr.gfc = dis[cr.idx];
                if(cr.hfc+cr.gfc>e)	continue;
                q.push(cr);
            }
    }
}
int main(){
    cin>>n>>m>>e;
    for(int i=1; i<=m; i++){
        scanf("%d %d %lf", &uu, &vv, &ww);
        add_edge(uu, vv, ww);
        add_edge(vv, uu, ww);
    }
    spfa();
    astar();
    cout<<ans<<endl;
    return 0;
}