【强连通】强连通模板 Tarjan

比起双连通的Tarjan我倒是觉得反而简单多了。思想和双连通分量是同一个模式。

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <stack>
using namespace std;

const int N = 1e5;
int dfn
, scc_id
;
int deep, scc_cnt;
stack <int> s;

int dfs(int u)
{
int lowu = dfn[u] = ++deep;
s.push(u);
for(int i = head[u]; ~i; i = e[i].next) {
int v = e[i].v;
if(!dfn[v]) {
int lowv = dfs(v);
lowu = min(lowu, lowv);
}
else if(!scc_id[v]) {//连到栈中的还未标号的祖先们
lowu = min(lowu, dfn[v]);
}//利用当前scc中的点来更新
}
if(lowu == dfn[u]) {//只有最先发现的点满足这个条件
scc_cnt++;
while(1) {
int x = s.top(); s.pop();
scc_id[x] = scc_cnt;
if(x == u) break;
}
}
return lowu;
}

void tarjan()
{
for(int i = 0; i < n; i++) {
dfn[i] = scc_id[i] = 0;
}
deep = scc_cnt = 0;
for(int i = 0; i < n; i++) {
if(!dfn[i]) dfs(i);
}
}

int main()
{

return 0;
}