[SDOI2010] 魔法猪学院

Description

给定e和边权，求有多少条不同的道路能从1到n使得边权之和的和小于e

Solution

A*裸题 娘的要是SPFA再把dis写成to就剁手

// By YoungNeal
#include<queue>
#include<cstdio>
#include<cstring>
#define int long long
using namespace std;

double e;
int ans,INF;
];
];
];
int n,m,cnt1,cnt2;
],head2[];

struct Edge1{
    int to,nxt;
    double dis;
}edge1[];

struct Edge2{
    int to,nxt;
    double dis;
}edge2[];

void add1(int x,int y,double z){
    edge1[++cnt1].to=y;
    edge1[cnt1].dis=z;
    edge1[cnt1].nxt=head1[x];
    head1[x]=cnt1;
}

void add2(int x,int y,double z){
    edge2[++cnt2].to=y;
    edge2[cnt2].dis=z;
    edge2[cnt2].nxt=head2[x];
    head2[x]=cnt2;
}

struct Node{
    int now;
    double f,dis;
    friend bool operator<(Node a,Node b){
        return a.dis+a.f>b.dis+b.f;
    }
};

queue<int> q;
priority_queue<Node> pq;

void spfa(int s){
    dis[s]=;
    q.push(s);
    while(q.size()){
        int u=q.front();q.pop();
        b[u]=;
        for(int i=head2[u];i;i=edge2[i].nxt){
            int to=edge2[i].to;
            if(dis[to]>dis[u]+edge2[i].dis){
                dis[to]=dis[u]+edge2[i].dis;
                if(!b[to]){
                    q.push(to);
                    b[to]=;
                }
            }
        }
    }
}

signed main(){
    scanf("%lld%lld%lf",&n,&m,&e);
    ;i<=n;i++) dis[i]=;
    ;i<=m;i++){
        int x,t;double q;
        scanf("%lld%lld%lf",&x,&t,&q);
        add1(x,t,q);add2(t,x,q);
    }
    spfa(n);
    INF=e/dis[];
    Node start;
    start.now=,start.f=dis[],start.dis=;
    pq.push(start);
    while(pq.size()){
        Node now=pq.top();pq.pop();
        if(now.now==n){
            e-=now.dis;
            ){
                printf("%lld",ans);
                ;
            }
            ans++;
            continue;
        }
        for(int i=head1[now.now];i;i=edge1[i].nxt){
            Node nxt;
            nxt.now=edge1[i].to;
            nxt.dis=now.dis+edge1[i].dis;
            nxt.f=dis[nxt.now];
            pq.push(nxt);
        }
    }
}