k短路模板 POJ2449

采用A*算法的k短路模板

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cstdlib>
#include <queue>
using namespace std;
const int MAXN=200005;
int init(){
	int rv=0,fh=1;
	char c=getchar();
	while(c<'0'||c>'9'){
		if(c=='-') fh=-1;
		c=getchar();
	}
	while(c>='0'&&c<='9'){
		rv=(rv<<3)+(rv<<1)+c-'0';
		c=getchar();
	}
	return rv*fh;
}
int disk[MAXN],s,t,k,dis[MAXN],head1[MAXN],head[MAXN],nume,n,m;
struct edge{
	int to,nxt,dis;
}e[MAXN],e1[MAXN];
void adde(int from,int to,int dis){
	e[++nume].to=to;
	e[nume].dis=dis;
	e[nume].nxt=head[from];
	head[from]=nume;
}
void adde1(int from,int to,int dis){
	e1[++nume].to=to;
	e1[nume].dis=dis;
	e1[nume].nxt=head1[from];
	head1[from]=nume;
}
struct cmp{
	bool operator ()(const int &a,const int &b) const {
		return dis[a]>dis[b];
	}
};
struct node{
	int v,f,g;
	bool operator < (const node &a)const{
		if(a.f==f) return a.g<g;
		return a.f<f;
	}
};
void dij(){
	priority_queue<int,vector<int>,cmp> q;
	memset(dis,0x3f,sizeof(dis));
	dis[t]=0;
	q.push(t);
	while(!q.empty()){
		int u=q.top();q.pop();
		for(int i=head1[u];i;i=e1[i].nxt){
			int v=e1[i].to;
			if(dis[v]>dis[u]+e1[i].dis){
				dis[v]=dis[u]+e1[i].dis;
				q.push(v);
			}
		}
	}
}
int A_star(){
	if(s==t) k++;
	int cnt[MAXN];
	if(dis[s]==0x3f3f3f3f) return -1;
	memset(cnt,0,sizeof(cnt));
	priority_queue <node> q;
	q.push({s,dis[s],0});
	while(!q.empty()){
		node u=q.top();q.pop();
		cnt[u.v]++;
		if(u.v==t&&cnt[u.v]==k) return u.g;
		if(cnt[u.v]>k) continue;
		for(int i=head[u.v];i;i=e[i].nxt){
			q.push({e[i].to,u.g+e[i].dis+dis[e[i].to],u.g+e[i].dis});
		}
	}
	return -1;
}
int main(){
	n=init();m=init();
	for(int i=1;i<=m;i++){
		int u=init(),v=init(),di=init();
		adde1(v,u,di);
	}
	s=init();t=init();k=init();
	dij();
	nume=0;
	for(int i=1;i<=n;i++){
		for(int j=head1[i];j;j=e1[j].nxt){
			adde(e1[j].to,i,e1[j].dis);
		}
	}
	//for(int i=1;i<=n;i++) for(int j=head[i];j;j=e[j].nxt) cout<<e[j].to<<endl;
	int ans=A_star();
//	cout<<dis[s]<<endl;
//	cout<<dis[t]<<endl;
	printf("%d\n",ans);
	return 0;
}