Tarjan算法之简单缩点

有向图

inline void tarjan(int x) {
	dfn[x] = low[x] = ++cnt;
	st[++top] = x;vis[x] = 1;
	for(rint i = head[x];i;i = e[i].last) {
		if(!dfn[e[i].to]) {
			tarjan(e[i].to);
			low[x] = Min(low[x],low[e[i].to]);
		}
		else if(vis[e[i].to]) low[x] = Min(low[x],dfn[e[i].to]);
	}
	if(dfn[x] == low[x]) {
		col[x] = ++col[0];
		vis[x] = 0;
		while(st[top] ^ x) {
			col[st[top]] = col[0];
			vis[st[top]] = 0;
			--top;
		}
		--top;
	}
	return ;
}

无向图

inline void tarjan(int x,int da) {
	dfn[x] = low[x] = ++cnt;
	st[++top] = x;
	vis[x] = 1;
	for(rint i = head[x];i;i = e[i].last) {
		if(e[i].to == da) continue;
		if(!dfn[e[i].to]) {
			tarjan(e[i].to,x);
			low[x] = Min(low[x],low[e[i].to]);
		}
		else low[x] = Min(low[x],dfn[e[i].to]);
	}
	if(dfn[x] == low[x]) {
		col[x] = ++col[0];
		vis[x] = 0;
		while(st[top] ^ x) {
			col[st[top]] = col[0];
			vis[st[top]] = 0;
			--top;
		}
		--top;
	}
	return ;
}