POJ 1236 强联通分量

链接：

http://poj.org/problem?id=1236

代码：

int index = 0;
int low[MAXN], dfn[MAXN];
int vis[MAXN], bel[MAXN];
VI G[MAXN];
stack<int> S;
int scc_cnt;

void tarjan(int u) {
    dfn[u] = low[u] = ++index;
    S.push(u); vis[u] = 1;
    rep(i, 0, G[u].size()) {
        int v = G[u][i];
        if (!dfn[v]) {
            tarjan(v);
            low[u] = min(low[u], low[v]);
        }
        else if (vis[v]) low[u] = min(low[u], dfn[v]);
    }
    if (low[u] == dfn[u]) {
        scc_cnt++;
        while (1) {
            int now = S.top(); S.pop();
            vis[now] = 0;
            bel[now] = scc_cnt;
            if (now == u) break;
        }
    }
}

int n;
int in[MAXN], out[MAXN];

void scc() {
    index = scc_cnt = 0;
    memset(dfn, 0, sizeof(dfn));
    rep(i, 0, n) if (!dfn[i]) tarjan(i);
}

int main() {
    cin >> n;
    int a;
    rep(i, 0, n) while (cin >> a, a) G[i].pb(a - 1);
    scc();
    if (scc_cnt == 1) {
        cout << 1 << endl << 0 << endl;
        return 0;
    }
    rep(u, 0, n) rep(i, 0, G[u].size()) {
        int v = G[u][i];
        if (bel[u] != bel[v]) {
            out[bel[u]]++;
            in[bel[v]]++;
        }
    }
    int in_tot = 0, out_tot = 0;
    rep(i, 1, scc_cnt + 1) {
        if (!in[i]) in_tot++;
        if (!out[i]) out_tot++;
    }
    cout << in_tot << endl << max(in_tot, out_tot) << endl;
    return 0;
}