POJ 2502 建图+spfa模版

九野的博客，转载请注明出处：http://blog.csdn.net/acmmmm/article/details/11895845

题意：第一行给定起末点坐标

下面每行输入地铁线路，(-1,-1)表示该线路输入结束，读到EOF

任意点都可达，速度是10km/h ,地铁线路上相邻2点速度是40km/h ，问最短时间是多少分钟

 

#include <cstdio>
#include <cstring>
#include <iostream>
#include <math.h>
#include <queue>
#define N 250
#define M N*N+2
#define inf64 0x7ffffff
#define inf 0x7ffffff
using namespace std;

inline int Min(int a,int b){return a>b?b:a;}
struct Edge{
	int f,t,nex;
	double d;
}edge[M];
int head[N],edgenum;
double dis[N];
struct node{
	double x,y;
}p[N];
double DIS(node a,node b){return sqrt((double)(a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));}
void addedge(int u,int v,double d){
	Edge E={u,v,head[u],DIS(p[u],p[v])*6/(d*100)};
	edge[edgenum]=E;
	head[u]=edgenum++;
}

int n;
void spfa(){
	int i,u,v;
	for(i=0;i<=n;i++)dis[i]=inf;
	bool inq[N]; memset(inq,0,sizeof(inq));
	dis[1]=0;
	queue<int>q;	q.push(1);	inq[1]=1;
	inq[2]=1;
	while(!q.empty()){
		u=q.front(); q.pop(); inq[u]=false;
		for(i=head[u];i!=-1;i=edge[i].nex)
		{
			v=edge[i].t;
			if(dis[v]>dis[u]+edge[i].d)
			{
				dis[v]=dis[u]+edge[i].d;
				if(!inq[v])
					q.push(v),inq[v]=1;
			}
		}
	}
}
int main()
{
	double x,y;
	memset(head,-1,sizeof(head)); edgenum=0;
	scanf("%lf %lf %lf %lf",&p[1].x,&p[1].y,&p[2].x,&p[2].y);

	n=3;
	int now=3;
	while(~ scanf("%lf%lf",&x,&y))
		if(x==-1 && y==-1)
		{
			for(int i=now;i<n-1;i++)addedge(i,i+1,40),addedge(i+1,i,40);
			now=n;
		}
		else 
		{
		p[n].x=x, p[n].y=y;
		n++;
		}

	for(int i=1;i<n;i++)
		for(int j=1;j<n;j++)
			if(i!=j)
			addedge(i,j,10);
	spfa();
	printf("%.0lf\n",dis[2]);

	return 0;
}
/*
0 0 10000 1000
0 200 5000 200 7000 200 -1 -1 
2000 600 5000 600 10000 600 -1 -1

*/