求解图的割点与桥

割点与桥详解地址
时间复杂度(|E| + |V|)
板子

int edge[MAXN][MAXN];
int bridge[MAXN][MAXN], cut[MAXN];
int low[MAXN], dfn[MAXN], vis[MAXN];
int ans;



void cut_bridge(int cur, int father, int dep, int n) {
    vis[cur] = 1;
    dfn[cur] = low[cur] = dep;
    int children = 0;
    for (int i = 0; i < n; i++) {
        if (edge[cur][i]) {
            if (i != father && 1 == vis[i]) {
                if (dfn[i] < low[cur]) {
                    low[cur] = dfn[i];
                }
            } else if (0 == vis[i]) {
                cut_bridge(i, cur, dep+1, n);
                children++;
                if (low[i] < low[cur]) {
                    low[cur] = low[i];
                }
                if ((father == -1 && children > 1) || (father != -1 && low[i] >= dfn[cur])) {
                    cut[cur] = true;
                }
                if (low[i] > dfn[cur]) {
                    bridge[cur][i] = bridge[i][cur] = true;
                }
            }
        }
    }
    vis[cur] = 2;
}