【题目链接】
【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; }