HDU2145 SPFA

题意：给定一些人，这些人要到同一个地点去，求最先到达的人。

spfa（反向加边就行） 水~

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<queue>
#include<algorithm>
using namespace std;
const int maxn = 315;
const int maxm = 5015;
const int inf = 9999999;
int cnt,head[ maxn ];
int n,m,k;
int dis[ maxn ],vis[ maxn ];
struct node{
    int u,val,next;
}edge[ maxm ];
struct node2{
    int city_number,dis;
    double speed,time;
    int p_number;//p_number is for the number of the people
}p[ maxn ];
void init(){
    cnt=0;
    memset( head,-1,sizeof( head ));
}
void addedge( int a,int b,int c ){
    edge[ cnt ].u=b;
    edge[ cnt ].val=c;
    edge[ cnt ].next=head[ a ];
    head[ a ]=cnt++;
}
int cmp( node2 a,node2 b ){
    if( a.time!=b.time )
        return a.time<b.time;
    else if( a.dis!=b.dis )
        return a.dis>b.dis;
    else
        //return a.city_number>b.city_number;
        return a.p_number>b.p_number;
}

void spfa( int s ){
    for( int i=1;i<=n;i++ ){
        dis[ i ]=inf;
        vis[ i ]=0;
    }
    queue<int>q;
    while( !q.empty() )
        q.pop();
    dis[ s ]=0;
    vis[ s ]=1;
    q.push( s );
    while( !q.empty() ){
        int now=q.front();
        q.pop();
        vis[ now ]=0;
        for( int i=head[ now ];i!=-1;i=edge[ i ].next ){
            int next=edge[ i ].u;
            if( dis[ next ]>dis[ now ]+edge[ i ].val ){
                dis[ next ]=dis[ now ]+edge[ i ].val;
                if( vis[ next ]==0 ){
                    vis[ next ]=1;
                    q.push( next );
                }
            }
        }
    }
    return ;
}

int main(){
    while( scanf("%d%d%d",&n,&m,&k)!=EOF ){
        int a,b,c;
        init();
        while( k-- ){
            scanf("%d%d%d",&a,&b,&c);
            addedge( b,a,c );//change the dir
        }
        int zz_pos;
        scanf("%d",&zz_pos);
        for( int i=1;i<=m;i++ ){
            scanf("%d",&p[i].city_number);
        }
        for( int i=1;i<=m;i++ ){
            scanf("%lf",&p[i].speed);
        }
        spfa( zz_pos );//the aim to all the vet,get dis[ maxn ]
        for( int i=1;i<=m;i++ ){
            p[i].p_number=i;
            if( dis[ p[i].city_number ]>=inf ){
                p[i].time=1.0*inf;
                p[i].dis=inf;
            }
            else{
                p[i].dis=dis[ p[i].city_number ];
                p[i].time=dis[ p[i].city_number ]*1.0/(1.0*p[i].speed);
            }
        }
        sort( p+1,p+1+m,cmp );
        if( p[1].time>=(1.0*inf) ){
            printf("No one\n");
        }
        else{
            printf("%d\n",p[1].p_number);
        }
    }
    return 0;
}