HDU 4318 Contest 2

简单的一题，使用类DIJK的算法就可以了。

#include <iostream>
#include <cstdio>
#include <queue>
#include <algorithm>
using namespace std;

struct Edge{
	int u,v;
	double lose;
	int next;
}edge[2500050];
int head[50010]; bool vis[50010];
int tot;
void addedge(int u,int v,double l){
	edge[tot].u=u;
	edge[tot].v=v;
	edge[tot].lose=l;
	edge[tot].next=head[u];
	head[u]=tot++;
}
double dist[50010];
struct point{
	int node;
	double power;
	bool operator < (const point &p)const {
		return power<p.power;
	}
}pushed,tmp;
priority_queue<point>que;

int main(){
	int n,v,l,f,t; double M;
	while(scanf("%d",&n)!=EOF){
		int k; tot=0;
		for(int i=1;i<=n;i++){
			head[i]=-1;
			vis[i]=false;
			dist[i]=0;
		}
		for(int u=1;u<=n;u++){
			scanf("%d",&k);
			for(int p=1;p<=k;p++){
				scanf("%d%d",&v,&l);
				addedge(u,v,l*1.0);
			}
		}
		scanf("%d%d%lf",&f,&t,&M);
		tmp.node=f; tmp.power=M;
		dist[f]=M;
		que.push(tmp);
		while(!que.empty()){
			tmp=que.top();
			if(tmp.node==t) break;
			que.pop();
			if(vis[tmp.node])
			continue;
			vis[tmp.node]=true;
			for(int e=head[tmp.node];e!=-1;e=edge[e].next){
				if(!vis[edge[e].v]){
					if(tmp.power*(1-edge[e].lose*1.0/100)>dist[edge[e].v]){
						dist[edge[e].v]=tmp.power*(1-edge[e].lose*1.0/100);
						pushed.node=edge[e].v;	pushed.power=dist[edge[e].v];
						que.push(pushed);
					}
				}
			}
		}
		if(dist[t]<1e-8)
		printf("IMPOSSIBLE!\n");
		else printf("%.2lf\n",M-dist[t]);
		while(!que.empty())
		que.pop();
	}
	return 0;
}