POJ 1523 SPF (cut point)

Approximate test instructions:  

a connected undirected graph is given to find out which points are cut points, and for each cut point, the number of connected components after the point is removed. Output "No SPF nodes" if there is no cut point.

Ideas:

Seek cutting point with Tarjan can, and then ask to delete the number of connected components after cutting point, every time to find a cut point, and then from the point of cut Dfs, you can also directly in the Tarjan algorithm to record the number of child. So if the cutting point is the root, then the answer is child, not the root of the cut point answer is child+1

188k0msc++2121b#include<cstdio> #include <iostream> #include <cstring> #include <algorithm >using namespace Std;const int N = 1010;int head[n];struct edge{int v,next;}    es[n*n];struct node{int u; int cnt;} Ans[n];int n;int cnt;int dfn[n],low[n];int index,top=0;bool vis[n];bool book[n];void tarjan (int u,int rt,int PA) {Dfn[u    ]=low[u]=++index;    int child=0;        for (int i=head[u];~i;i=es[i].next) {int v=es[i].v;            if (dfn[v]==0) {Tarjan (v,rt,u);            Low[u]=min (Dfn[u],low[v]);        if (Low[v]>=dfn[u]) child++;    } if (V!=PA) low[u]=min (Dfn[u],low[v]);    } if (u==rt&&child>1) Ans[++top].u=u,ans[top].cnt=child; else if (u!=rt&&child) ans[++top].u=u,ans[top].cnt=child+1;}    void Ini () {memset (head,-1,sizeof (head));    cnt=0;    N=-1;    memset (dfn,0,sizeof (DFN));    memset (book,0,sizeof (book)); top=index=0;} BOOL CMP (const node &a,const node&b) {return a.u<b.u;} Int Main () {int u,v;    int cas=0;        while (scanf ("%d%d", &u,&v) = = 2) {printf ("Network #%d\n", ++cas);        INI ();        N=max (N,u);        N=max (V,n);        Es[++cnt].v=v;        Es[cnt].next=head[u];        head[u]=cnt;        Es[++cnt].v=u;        ES[CNT].NEXT=HEAD[V];        head[v]=cnt;            while (1) {scanf ("%d", &u);            if (u==0) break;            scanf ("%d", &v);            Es[++cnt].v=v;            Es[cnt].next=head[u];            head[u]=cnt;            Es[++cnt].v=u;            ES[CNT].NEXT=HEAD[V];            head[v]=cnt;        N=max (Max (u,v), n);        } for (int i=1;i<=n;i++) if (dfn[i]==0) Tarjan (i,i,-1);        Sort (ans+1,ans+1+top,cmp);        if (top==0) printf ("No SPF nodes\n");        for (int i=1;i<=top;i++) {printf ("SPF node%d leaves%d subnets\n", ans[i].u,ans[i].cnt);    } puts (""); } return 0;}

POJ 1523 SPF (cut point)