【POJ 1144】 Network

【题目链接】

            点击打开链接

【算法】

          Tarjan算法求割点

【代码】

          

#include <algorithm>
#include <bitset>
#include <cctype>
#include <cerrno>
#include <clocale>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <limits>
#include <list>
#include <map>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <utility>
#include <vector>
#include <cwchar>
#include <cwctype>
#include <stack>
#include <limits.h>
using namespace std;
#define MAXN 110
#define MAXM 10010

struct Edge
{
        int to,nxt;
} e[MAXM];

int n,i,u,v,timer,ans,tot;
bool is_cut[MAXN];
int head[MAXN],low[MAXN],dfn[MAXN];

inline void add(int u,int v)
{
        tot++;
        e[tot] = (Edge){v,head[u]};
        head[u] = tot;
}
inline void tarjan(int u,int fa)
{
        int i,v,son = 0;
        dfn[u] = low[u] = ++timer;
        for (i = head[u]; i; i = e[i].nxt)
        {
                v = e[i].to;
                if (fa != v)
                {
                        if (!dfn[v])
                        {
                                tarjan(v,u);
                                low[u] = min(low[u],low[v]);
                                if (low[v] >= dfn[u]) son++;         
                        }    else low[u] = min(low[u],dfn[v]);
                }        
        }    
        if (u != 1 && son) is_cut[u] = true;
        else if (u == 1 && son > 1) is_cut[u] = true;
        else is_cut[u] = false;
}

int main() 
{
        
        while (scanf("%d",&n) != EOF && n)
        {
                tot = 0;
                timer = 0;
                ans = 0;
                for (i = 1; i <= n; i++) 
                {
                        dfn[i] = low[i] = 0;
                        head[i] = 0;
                        is_cut[i] = false;
                }
                while (scanf("%d",&u) && u)
                {
                        while (getchar() != '
')
                        {
                                scanf("%d",&v);
                                add(u,v);
                                add(v,u);        
                        }    
                }    
                tarjan(1,-1);
                for (i = 1; i <= n; i++)
                {
                        if (is_cut[i])
                                ans++;
                }
                printf("%d
",ans);
        }
        
        return 0;
    
}