HDU1535 spfa

题意 给定一张图，计算从1到各点的最短距离+各点到1的最短距离。

spfa即可，分别正向，反向建一个图。

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 = 1000005;

  8 const int maxm = 1000015;

  9 const int inf = 99999999;

 10 int cnt1,cnt2,head1[ maxn ],head2[ maxn ];

 11 struct node{

 12     int u,val,next;

 13 }edge1[ maxm ],edge2[ maxm ];

 14 int n,m;

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

 16 void init(){

 17     cnt1=cnt2=0;

 18     memset( head1,-1,sizeof( head1 ));

 19     memset( head2,-1,sizeof( head2 ));

 20     //printf("%d\n",inf);

 21 }

 22 void addedge1( int a,int b,int c ){

 23     edge1[ cnt1 ].u=b;

 24     edge1[ cnt1 ].val=c;

 25     edge1[ cnt1 ].next=head1[ a ];

 26     head1[ a ]=cnt1++;

 27 }

 28 void addedge2( int a,int b,int c ){

 29     edge2[ cnt2 ].u=b;

 30     edge2[ cnt2 ].val=c;

 31     edge2[ cnt2 ].next=head2[ a ];

 32     head2[ a ]=cnt2++;

 33 }

 34 void spfa1( int s ){

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

 36         dis[ i ]=inf;

 37         vis[ i ]=0;

 38     }

 39     queue<int>q;

 40     while( !q.empty() )

 41         q.pop();

 42     dis[ s ]=0;

 43     vis[ s ]=1;

 44     q.push( s );

 45     while( !q.empty() ){

 46         int now=q.front();

 47         q.pop();

 48         vis[ now ]=0;

 49         for( int i=head1[ now ];i!=-1;i=edge1[ i ].next ){

 50             int next=edge1[ i ].u;

 51             if( dis[ next ]>dis[ now ]+edge1[ i ].val ){

 52                 dis[ next ]=dis[ now ]+edge1[ i ].val;

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

 54                     vis[ next ]=1;

 55                     q.push( next );

 56                 }

 57             }

 58         }

 59     }

 60     return ;

 61 }

 62 void spfa2( int s ){

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

 64         dis[ i ]=inf;

 65         vis[ i ]=0;

 66     }

 67     queue<int>q;

 68     while( !q.empty() )

 69         q.pop();

 70     dis[ s ]=0;

 71     vis[ s ]=1;

 72     q.push( s );

 73     while( !q.empty() ){

 74         int now=q.front();

 75         q.pop();

 76         vis[ now ]=0;

 77         for( int i=head2[ now ];i!=-1;i=edge2[ i ].next ){

 78             int next=edge2[ i ].u;

 79             if( dis[ next ]>dis[ now ]+edge2[ i ].val ){

 80                 dis[ next ]=dis[ now ]+edge2[ i ].val;

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

 82                     vis[ next ]=1;

 83                     q.push( next );

 84                 }

 85             }

 86         }

 87     }

 88     return ;

 89 }

 90 int main(){

 91     int ca;

 92     scanf("%d",&ca);

 93     while( ca-- ){

 94         init();

 95         scanf("%d%d",&n,&m);

 96         int a,b,c;

 97         while( m-- ){

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

 99             addedge1( a,b,c );

100             addedge2( b,a,c );

101         }

102         int ans=0;

103         spfa1( 1 );

104         //printf("spfa1:\n");

105         for( int i=2;i<=n;i++ ){

106             //printf("dis[%d]=%d \n",i,dis[i]);

107             ans+=dis[ i ];

108         }

109         spfa2( 1 );

110         //printf("spfa2:\n");

111         for( int i=2;i<=n;i++ ){

112         //    printf("dis[%d]=%d \n",i,dis[i]);

113             ans+=dis[ i ];

114         }

115         printf("%d\n",ans);

116     }

117     return 0;

118 }