Tarjian【Template】

#include<iostream>#include<cstring>using namespace std;const int M = 1e5 + 7;const int N = 1e5 + 7;struct node {    int v;    int nxt;}e[M];int head[N], cnt;int p[N], st[N], id, top, scc;int dfn[N], low[N], belong[N];void add(int u, int v){    e[cnt].v = v, e[cnt].nxt = head[u];    head[u] = cnt++;}void init(){    memset(head, -1, sizeof(head));    memset(p, 0, sizeof(p));    memset(dfn, 0, sizeof(dfn));    id = top = cnt = 0;}void dfs(int u){    dfn[u] = low[u] = ++id;    st[++top] = u, p[u] = 1;    int v;    for (int i = head[u]; i != -1; i = e[i].nxt)    {        v = e[i].v;        if (!dfn[v])        {            dfs(v);            if (low[v] < low[u])                low[u] = low[v];        }        else if (p[v] && dfn[v] < low[u])        {            low[u] = dfn[v];        }    }    if (dfn[u] == low[u])    {        ++scc;        do {            v = st[top--];            p[v] = 0;            belong[v] = scc;        } while (v != u);    }}void Tarjian(int n){    for (int i = 1; i <= n; i++)    {        if (!dfn[i])            dfs(i);    }    cout << scc << endl;    for (int i = 1; i <= n; i++)    {        cout << i << " " << belong[i] << endl;    }}int main(){    int n, m, u, v;    cin >> n >> m;    init();    while (m--)    {        cin >> u >> v;        add(u, v);    }    Tarjian(n);    return 0;}