HDU1224 SPFA

题意：给定一张图，求从1到n+1的最长距离。

bfs即可，没什么技巧。

View Code

  1 #include<stdio.h>

  2 #include<string.h>

  3 #include<stdlib.h>

  4 #include<algorithm>

  5 #include<queue>

  6 #include<stack>

  7 using namespace std;

  8 const int maxn = 105;

  9 const int maxm = 10000;

 10 const int inf = 99999999;

 11 int cnt,head[ maxn ];

 12 struct node{

 13     int u,val,next;

 14 }edge[ maxm ];

 15 int n,m;

 16 int val[ maxn ];

 17 int dis[  maxn ],vis[ maxn ],path[ maxn ];

 18 

 19 void init(){

 20     cnt=0;

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

 22 }

 23 

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

 25     edge[ cnt ].u=b;

 26     edge[ cnt ].val=c;

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

 28     head[ a ]=cnt++;

 29 }

 30 

 31 void bfs(){

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

 33         vis[i]=0;

 34         dis[i]=-inf;

 35         path[i]=-1;

 36     }

 37     queue<int>q;

 38     while( !q.empty() )

 39         q.pop();

 40     q.push( 1 );

 41     vis[1]=1;

 42     dis[1]=0;

 43     while( !q.empty() ){

 44         int now=q.front();

 45         q.pop();

 46         vis[ now ]=0;

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

 48             int next=edge[i].u;

 49             if( dis[next]<dis[now]+val[next] ){

 50                 dis[next]=dis[now]+val[next];

 51                 path[next]=now;

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

 53                     vis[next]=1;

 54                     q.push(next);

 55                 }

 56             }

 57         }

 58     }

 59 }

 60 void output(){

 61     printf("points : %d\n",dis[n+1]);

 62     stack<int>s;

 63     for( int i=n+1;i!=-1;i=path[i] ){

 64         s.push( i );

 65     }

 66     printf("circuit : ");

 67     printf("%d",s.top());

 68     s.pop();

 69     while( !s.empty() ){

 70         if( s.top()==(n+1) )

 71             printf("->%d",1);

 72         else

 73             printf("->%d",s.top());

 74         s.pop();

 75     }

 76     printf("\n");

 77 }

 78 int main(){

 79     int T;

 80     scanf("%d",&T);

 81     for( int ca=1;ca<=T;ca++ ){

 82         if( ca!=1 )

 83             printf("\n");

 84         scanf("%d",&n);

 85         for( int i=1;i<=n;i++ )

 86             scanf("%d",&val[ i ]);

 87         val[n+1]=0;

 88         scanf("%d",&m);

 89         int a,b;

 90         init();

 91         while( m-- ){

 92             scanf("%d%d",&a,&b);

 93             if( a<b ){

 94                 addedge( a,b,0 );

 95             }

 96             else if( a>b ){

 97                 addedge( b,a,0 );

 98             }

 99         }

100         bfs();

101         printf("CASE %d#\n",ca);

102         //printf("%d\n",dis[n+1]);

103         output();

104     }

105     return 0;

106 }