【连通图】无向图关节点和桥 Tarjan

#include <cstdio> #include <cstring> #include <algorithm> using namespace std;  const int N = 1e5, M = 1e5; struct Edge {     int v, next, idx;     Edge(){}     Edge(int _v, int _next, int _idx):         v(_v), next(_next), idx(_idx){} }e[M]; int low[N], dfn[N], deep, head[N], tot; bool iscut[N], isbri[M];  void __init__() {     tot = deep = 0;     memset(head, -1, sizeof(head));     memset(iscut, 0, sizeof(iscut)); }  void add(int u, int v, int idx) {     e[tot++] = Edge(v, head[u], idx);     head[u] = tot++; }  int dfs(int u, int fa) {     int lowu = dfn[u] = ++deep;     int cnt = 0;     for(int i = head[u]; ~i; i = e[i].next) {         int v = e[i].v;         if(!dfn[v]) {             cnt++;             int lowv = dfs(v, u);             lowu = min(lowu, lowv);             if(lowv >= dfn[u]) iscut[u] = true;             if(lowv > dfn[u]) isbri[e[i].idx] = true;             continue ;         }         if(dfn[v] < dfn[u] && v != fa)             lowu = min(lowu, dfn[v]);     }     if(fa == -1 && cnt == 1) iscut[u] = false;     return low[u] = lowu; }  int main() {     __init__();     return 0; }