POJ-1523 SPF 割点

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题意：给你幅图，求割点对每个点去掉后联通分量数；

裸Tarjan

#include<stdio.h>#include<string.h>#include<vector>#include<queue>using namespace std;const int maxn = 1025;const int inf = 1<<29;int n,son;vector<int>map[maxn];int dfs_clock,low[maxn],dfn[maxn];int iscut[maxn];void dfs( int u,int fa ){low[u] = dfn[u] = ++dfs_clock;for( int i = 0; i < map[u].size(); i ++ ){int v = map[u][i];if( !dfn[ v ] ){dfs(v,u);low[u] = low[u] <= low[v] ? low[u]:low[v];if( low[v] >= dfn[u] ){if( fa != -1 )iscut[u] ++;elseson ++;}}else if( dfn[v] < dfn[u] && v != fa )              low[u] = low[u] <= dfn[v] ? low[u]:dfn[v];  }}void tarjan(){dfs_clock = 0,son = 0;memset( low,0,sizeof(low) );      memset( dfn,0,sizeof(dfn) );      memset( iscut,0,sizeof(iscut) );dfs(1,-1);if( son > 1 )iscut[1] = son - 1;}int main(){    //freopen("data.txt","r",stdin);int cas = 0,u,v;while( scanf("%d",&u) != EOF,u ){scanf("%d",&v);for( int i = 1; i <= 1000; i ++ )              map[i].clear();  map[u].push_back( v );map[v].push_back( u );n = u >= v?u:v;while( scanf("%d",&u) == 1 && u ){scanf("%d",&v);map[u].push_back( v );map[v].push_back( u );n = u >= v?u:v;}tarjan();int flag = 0;if( cas )puts("");printf("Network #%d\n",++cas);for( int i = 1; i <= n; i ++ ){if( iscut[i] ){flag = 1;printf("  SPF node %d leaves %d subnets\n",i,iscut[i]+1);}}if( !flag )printf("  No SPF nodes\n");}    return 0;}