poj 2449 Remmarguts' Date 第K短路

题意：给一个有向图，告诉起点和终点，求第K短路

解法：dijkstra+A*，正反两个邻接表

总结：做完这个题学会了dijkstra算法，对A*有了一点了解

PS.优先队列里的比较函数变量写错了，MLE了3天，恶心死我了。膜拜无语神牛，几分钟就指导我搞定了

/*

Problem: 2449		User: fancy081

Memory: 6472K		Time: 250MS

Language: C++		Result: Accepted

*/

#include<cstdio>

#include<queue>

#include<cstring>

using namespace std;



const int MAXN=1005;

const int MAXM=100005;

const int INF=100000000;



int N,M,Start,Te,Kth;

short v[MAXM],rev[MAXM],w[MAXM];

int next[MAXM];

int renext[MAXM];

int first[MAXN],refirst[MAXN];

int h[MAXN];



struct nod

{

	int len,pos;

	bool operator<(const nod &x)const

	{

		return x.len<len;

	}

};

priority_queue<nod> Que;



void dijkstra()

{

	bool done[MAXN];

	while(!Que.empty()) Que.pop();

	for(int i=1;i<=N;i++) {h[i]=INF;done[i]=false;}

	h[Te]=0;	

	nod tmp,iq;

	tmp.len=0;tmp.pos=Te;

	Que.push(tmp);

	int uu,vv,dd;

	while(!Que.empty())

	{

		tmp=Que.top();Que.pop();

		uu=tmp.pos;

		if(done[uu]) continue;

		dd=tmp.len;

		done[uu]=true;

		for(vv=refirst[uu];vv!=-1;vv=renext[vv])

		{

			if(dd+w[vv]<h[rev[vv]])

			{

				h[rev[vv]]=dd+w[vv];

				iq.len=h[rev[vv]];

				iq.pos=rev[vv];

				Que.push(iq);			

			}

		}

	}

}



struct nodx

{

	int f,pos;

	bool operator<(const nodx &x)const

	{

		return x.f<f;

	}

};

priority_queue<nodx> Quex;

int astar()

{

	nodx tmp,iq;

	while(!Quex.empty()) Quex.pop();

	int cnt[MAXN];

	for(int i=1;i<=N;i++) cnt[i]=0;

	tmp.f=h[Start];tmp.pos=Start;

	Quex.push(tmp);

	int ff,now,gg,vv;

	while(!Quex.empty())

	{

		tmp=Quex.top();Quex.pop();

		ff=tmp.f;now=tmp.pos;

		gg=tmp.f-h[now];

		cnt[now]++;

		if(cnt[now]>Kth) continue;

		if(cnt[Te]==Kth) return ff;

		for(vv=first[now];vv!=-1;vv=next[vv])

		{

			iq.f=gg+w[vv]+h[v[vv]];

			iq.pos=v[vv];

			Quex.push(iq);

		}

	}

	return -1;

}



int main()

{

	while(scanf("%d%d",&N,&M)!=EOF)

	{

		for(int i=0;i<=N;i++) {first[i]=-1;refirst[i]=-1;}

		for(int e=0;e<M;e++)

		{

			scanf("%d%d%d",&rev[e],&v[e],&w[e]);

			next[e]=first[rev[e]];

			first[rev[e]]=e;

			renext[e]=refirst[v[e]];

			refirst[v[e]]=e;

		}		

		scanf("%d%d%d",&Start,&Te,&Kth);

		if(Start==Te) Kth++;

		dijkstra();

	        printf("%d\n",astar());

	}

	return 0;

}