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~

View Code

  1 #include<stdio.h>

  2 #include<string.h>

  3 #include<stdlib.h>

  4 #include<queue>

  5 #include<algorithm>

  6 using namespace std;

  7 const int maxn = 315;

  8 const int maxm = 5015;

  9 const int inf = 9999999;

 10 int cnt,head[ maxn ];

 11 int n,m,k;

 12 int dis[ maxn ],vis[ maxn ];

 13 struct node{

 14     int u,val,next;

 15 }edge[ maxm ];

 16 struct node2{

 17     int city_number,dis;

 18     double speed,time;

 19     int p_number;//p_number is for the number of the people

 20 }p[ maxn ];

 21 void init(){

 22     cnt=0;

 23     memset( head,-1,sizeof( head ));

 24 }

 25 void addedge( int a,int b,int c ){

 26     edge[ cnt ].u=b;

 27     edge[ cnt ].val=c;

 28     edge[ cnt ].next=head[ a ];

 29     head[ a ]=cnt++;

 30 }

 31 int cmp( node2 a,node2 b ){

 32     if( a.time!=b.time )

 33         return a.time<b.time;

 34     else if( a.dis!=b.dis )

 35         return a.dis>b.dis;

 36     else

 37         //return a.city_number>b.city_number;

 38         return a.p_number>b.p_number;

 39 }

 40 

 41 void spfa( int s ){

 42     for( int i=1;i<=n;i++ ){

 43         dis[ i ]=inf;

 44         vis[ i ]=0;

 45     }

 46     queue<int>q;

 47     while( !q.empty() )

 48         q.pop();

 49     dis[ s ]=0;

 50     vis[ s ]=1;

 51     q.push( s );

 52     while( !q.empty() ){

 53         int now=q.front();

 54         q.pop();

 55         vis[ now ]=0;

 56         for( int i=head[ now ];i!=-1;i=edge[ i ].next ){

 57             int next=edge[ i ].u;

 58             if( dis[ next ]>dis[ now ]+edge[ i ].val ){

 59                 dis[ next ]=dis[ now ]+edge[ i ].val;

 60                 if( vis[ next ]==0 ){

 61                     vis[ next ]=1;

 62                     q.push( next );

 63                 }

 64             }

 65         }

 66     }

 67     return ;

 68 }

 69 

 70 int main(){

 71     while( scanf("%d%d%d",&n,&m,&k)!=EOF ){

 72         int a,b,c;

 73         init();

 74         while( k-- ){

 75             scanf("%d%d%d",&a,&b,&c);

 76             addedge( b,a,c );//change the dir

 77         }

 78         int zz_pos;

 79         scanf("%d",&zz_pos);

 80         for( int i=1;i<=m;i++ ){

 81             scanf("%d",&p[i].city_number);

 82         }

 83         for( int i=1;i<=m;i++ ){

 84             scanf("%lf",&p[i].speed);

 85         }

 86         spfa( zz_pos );//the aim to all the vet,get dis[ maxn ]

 87         for( int i=1;i<=m;i++ ){

 88             p[i].p_number=i;

 89             if( dis[ p[i].city_number ]>=inf ){

 90                 p[i].time=1.0*inf;

 91                 p[i].dis=inf;

 92             }

 93             else{

 94                 p[i].dis=dis[ p[i].city_number ];

 95                 p[i].time=dis[ p[i].city_number ]*1.0/(1.0*p[i].speed);

 96             }

 97         }

 98         sort( p+1,p+1+m,cmp );

 99         if( p[1].time>=(1.0*inf) ){

100             printf("No one\n");

101         }

102         else{

103             printf("%d\n",p[1].p_number);

104         }

105     }

106     return 0;

107 }