洛谷 [P2483] [模板] k短路

人生中的第一道黑题。。。
其实就是k短路模板

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <cstdlib>
#include <queue>
using namespace std;
const int MAXN=400005;
int init(){
    int rv=0,fh=1;
    char c=getchar();
    while(c<'0'||c>'9'){
        if(c=='-') fh=-1;
        c=getchar();
    }
    while(c>='0'&&c<='9'){
            rv=(rv<<1)+(rv<<3)+c-'0';
            c=getchar();
        }
        return rv*fh;
    }
    int m,n,head1[MAXN],nume,head[MAXN];
    double tot,dis[MAXN];
    struct edge{
        int to,nxt;
        double dis;
    }e[MAXN],e1[MAXN];
    void adde1(int from,int to,double dis){
        e1[++nume].to=to;
        e1[nume].dis=dis;
        e1[nume].nxt=head1[from];
        head1[from]=nume;
    }
    void adde(int from,int to,double dis){
        e[++nume].to=to;
        e[nume].dis=dis;
        e[nume].nxt=head[from];
        head[from]=nume;
    }
    struct cmp{
        bool operator ()(const int &a,const int &b) const{
            return dis[a]>dis[b];
        }
    };
    void dij(){
        priority_queue <int,vector<int> ,cmp> q;
        q.push(n);
        memset(dis,0x7f,sizeof(dis));
        dis[n]=0;
        while(!q.empty()){
            int u=q.top();q.pop();
            for(int i=head1[u];i;i=e1[i].nxt){
                int v=e1[i].to;
                if(dis[v]>dis[u]+e1[i].dis){
                    dis[v]=dis[u]+e1[i].dis;
                    q.push(v);
                }
            }
        }
    }
    struct node{
        int v;
        double f,g;
        bool operator < (const node &a)const{
            if(this->f==a.f) return (this->g)>a.g;
            return (this->f)>a.f;
    }
};
void A_star(){
    node s;
    int cnt=0;
    s.v=1;s.f=dis[1];s.g=0.0;
    priority_queue <node>q;
    q.push(s);
    while(!q.empty()){
        node u=q.top();q.pop();//cout<<u.v<<" "<<u.f<<" "<<u.g<<endl;
        if(u.v==n){
            //cout<<tot<<endl;
            if(tot>=u.g) tot-=u.g,cnt++;
            else{
                cout<<cnt<<endl;
                return;
            }
        }
        for(int i=head[u.v];i;i=e[i].nxt){
            node v;
            v.v=e[i].to;
            v.g=u.g+e[i].dis;
            v.f=v.g+dis[e[i].to];
            //if(v.v==n) cout<<v.f<<endl;
            q.push(v);
        }
    }
    cout<<1<<endl;
}
int main(){
    n=init();m=init();scanf("%lf",&tot);
    for(int i=1;i<=m;i++){
        int u=init(),v=init();
        double di;
        scanf("%lf",&di);
        adde1(v,u,di);
    }
    dij();
//  cout<<dis[1]<<endl;
    nume=0;
    for(int i=1;i<=n;i++){
        for(int j=head1[i];j;j=e1[j].nxt){
            int v=e1[j].to;
            adde(v,i,e1[j].dis);
        }
    }
    //cout<<e[1].dis<<endl;
//  for(int i=head[1];i;i=e[i].nxt) cout<<e[i].to<<endl;
    A_star();
    return 0;
}

原文地址：https://www.cnblogs.com/Mr-WolframsMgcBox/p/8215027.html