poj1523解题报告

题意就是要求割点

用tarjan求强连通

#include <iostream>#include <cstring>using namespace std ;const int MAXN = 1100 ; const int MAXM = MAXN * MAXN ; struct type{int  to , next ; } ; type  edge[MAXM] ; int   head[MAXN] , Count , low[MAXN] , dfn[MAXN] , stack[MAXN] , top , ans[MAXN] , vis[MAXN] , son ; void  addedge( int start , int end ){edge[Count].to = end ; edge[Count].next = head[start] ; head[start] = Count ++ ; }void  tarjan_dfs( int cur , int father , int &cnt , int &Time ){dfn[cur] = low[cur] = Time ++ ;vis[cur] = 1 ; for( int i = head[cur] ; i != -1 ; i = edge[i].next ){int  v = edge[i].to ;if( v == father ) continue ;if( !vis[v] ){tarjan_dfs( v , cur , cnt , Time ) ; low[cur] = min( low[cur] , low[v] ) ;if( dfn[cur] <= low[v] ){ans[cur] ++ ;}}else low[cur] = min( low[cur] , dfn[v] ) ;}}int   tarjan( int n ){int   Time = 0 , cnt = 0 ;top = 0 ; memset( dfn , 0 , sizeof( dfn ) ) ; memset( low , 0 , sizeof( low ) ) ;memset( vis , 0 , sizeof( vis ) ) ; tarjan_dfs( 1 , -1 , cnt , Time ) ; return cnt ; }int main(){int  start , end , Max , cnt = 1 ; while( 1 ){memset( head , -1 , sizeof( head ) ) ;Count = 0 ;int  flag = 0 ;Max = 0 ;while( cin >> start ){if( start ) flag = 1 ;if( !start ) break ;cin >> end ;if( start > Max ) Max = start ;if( end > Max ) Max = end ;addedge( start , end ) ;addedge( end , start ) ;}if( !flag ) break ;son = 0 ; for( int i = 2 ; i <= Max ; i ++ ) ans[i] = 1 ; ans[1] = 0 ; tarjan( Max ) ;cout << "Network #" << cnt << endl ;cnt ++ ;flag = 0 ;for( int i = 1 ; i <= Max ; i ++ ){if( ans[i] > 1 ){cout << "  SPF node " << i << " leaves " << ans[i] << " subnets" << endl ;flag = 1 ;}}if( !flag ) cout << "  No SPF nodes" << endl ;cout << endl ; }return 0 ; }