Featured image of post [模板]强连通分量

[模板]强连通分量

Kosaraju

rg: 反图

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int n, m, comp[N];
vi g[N], rg[N];
bool vis[N];
vi s;

void dfs(int u) {
    vis[u] = true;
    for (auto v : g[u])
        if (!vis[v]) dfs(v);
    s.push_back(u);
}

void rdfs(int u, int k) {
    comp[u] = k;
    for (auto v : rg[u])
        if (!comp[v]) rdfs(v, k);
}

void kosaraju() {
    for (int i = 1; i <= n; i++)
        if (!vis[i]) dfs(i);
    int cnt = 0;
    for (int i = s.size() - 1; i >= 0; i--)
        if (!comp[s[i]]) rdfs(s[i], ++cnt);
}

int main() {
#ifndef ONLINE_JUDGE
    freopen("data/in.txt", "r", stdin);
    freopen("data/out.txt", "w", stdout);
#endif
    ios::sync_with_stdio(false);
    cin >> n >> m;
    for (int i = 1; i <= m; i++) {
        int u, v;
        cin >> u >> v;
        g[u].push_back(v);
        rg[v].push_back(u);
    }
    kosaraju();
    for (int i = 1; i <= n; i++) cout << comp[i] << " ";
    return 0;
}
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