UVA315 Network

Concept cut point: For an undirected graph, delete the edge points connected thereto, the overall increase in the number of connected components of FIG.

Tarjan algorithm for undirected graph, the precursor must be provided -

Seeking a cut point of the template -

#include<cstdio>
#include<algorithm>
#include<vector>
#include<stack>
#include<cstring>
using namespace std;
const int maxn=1014;
vector<int> g[maxn];
int N,M,x,y; 
int low[maxn];
int dfn[maxn];
int cnt;
int scc;
int pos[maxn];
int isGedian[maxn];
int isRoot[maxn];
stack<int> st;
void init () {
    fill (low,low+maxn,0);
    fill (dfn,dfn+maxn,0);
    fill (pos,pos+maxn,0);
    fill (isGedian,isGedian+maxn,0);
    for (int i=0;i<maxn;i++) g[i].clear();
    while (!st.empty()) st.pop();
    cnt=0;
    scc=0;
}
void tarjan (int x,int pre) {
    low[x]=dfn[x]=++cnt;
    int son=0;
    st.push(x);
    for (int i=0;i<g[x].size();i++) {
        if (g[x][i]==pre) continue;
        if (!low[g[x][i]]) {
            son++;
            tarjan(g[x][i],x);
            low[x]=min(low[x],low[g[x][i]]);
            if (x!=pre&&dfn[x]<=low[g[x][i]]) isGedian[x]=1;
        }
        else if (!pos[g[x][i]]) low[x]=min(low[x],dfn[g[x][i]]);
    }
    if (low[x]==dfn[x]) {
        scc++;
        while (1) {
            int u=st.top();
            st.pop();
            low[u]=low[x];
            pos[u]=scc;
            if (u==x) break;
        }
    }
    if (x==pre&&son>1) isGedian[x]=1;
}
int main () {
    while (scanf("%d",&N)&&N) {
        init ();
        while (scanf("%d",&x)&&x) {
            char ch;
            while ((ch=getchar())!='\n') {
                scanf ("%d",&y);
                g[x].push_back(y);
                g[y].push_back(x);
            }
        }
        for (int i=1;i<=N;i++) 
        if (!low[i]) tarjan(i,i);
        int gedian=0;
        for (int i=1;i<=N;i++) 
        if (isGedian[i]) gedian++;
        printf ("%d\n",gedian);
    }
    return 0;
}