P1266 速度限制

算法标签：最短路+DP

难度：提高+/省选-

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>
#include <algorithm>
#include <queue>
using namespace std;
#define N 155
#define M 25010
#define V 505
int n,m,d,cnt,h[N],v[N][V];
double f[N][V];
struct NodeA
{
	int nxt,to,l,v;
}e[M];
struct NodeB
{
	int x,y;
}lst[N][V];
queue <NodeB> q;

void AddEdge (int x,int y,int v,int l)
{
	e[++cnt].nxt=h[x];h[x]=cnt;
	e[cnt].to=y;e[cnt].v=v;e[cnt].l=l;
}

void Init ()
{
	scanf ("%d %d %d",&n,&m,&d);
	for (int i=1;i<=m;i++)
	{
		int x,y,v,l;
		scanf ("%d %d %d %d",&x,&y,&v,&l);
		AddEdge (x,y,v,l);
	}
}

void SPFA ()
{
	memset (f,127,sizeof (f));
	memset (lst,-1,sizeof (lst));
	f[0][70]=0;
	NodeB s;
	s.x=0;s.y=70;
	q.push (s);
	v[0][70]=1;
	while (!q.empty ())
	{
		int x=q.front ().x;
		int v1=q.front ().y;
		q.pop ();
		v[x][v1]=0;
		for (int i=h[x];i;i=e[i].nxt)
		{
			int y=e[i].to,v2=e[i].v,l=e[i].l;
			if (v2==0) v2=v1;
			if (f[x][v1]+l*1.0/v2<f[y][v2])
			{
				f[y][v2]=f[x][v1]+l*1.0/v2;
				lst[y][v2].x=x;lst[y][v2].y=v1;
				if (v[y][v2]==0)
				{
					NodeB s;
					s.x=y;s.y=v2;
					q.push (s);
					v[y][v2]=1;
				}
			}
		}
	}
}

void Print (int x,int v)
{
	if (x==-1) return;
	Print (lst[x][v].x,lst[x][v].y);
	printf ("%d ",x);
}

void Work ()
{
	SPFA ();
	int ans=0;
	for (int i=1;i<V;i++)
		if (f[d][ans]>f[d][i]) ans=i;
	Print (d,ans);
	putchar ('\n');
}

int main ()
{
	Init ();
	Work ();
	return 0;
}