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1236. Network of Schools
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POJ/1236/1236.cpp
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75
POJ/1236/1236.cpp
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#include <iostream>
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#include <stack>
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#include <vector>
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using std::cin;
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using std::cout;
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using std::endl;
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// Limits
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const int N = 105;
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int n, x, ans1, ans2;
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std::vector<int> g[N];
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int din[N], dout[N]; // 图的入度、出度
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// Tarjan
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int cnt, dfn[N], low[N];
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int scc_cnt, id[N];
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std::stack<int> st;
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bool vis[N];
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void tarjan(int u) {
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dfn[u] = low[u] = ++cnt;
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st.push(u);
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vis[u] = true;
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for (int i = 0; i < g[u].size(); i++) {
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int v = g[u][i];
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if (!dfn[v]) {
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tarjan(v);
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low[u] = std::min(low[u], low[v]);
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} else if (vis[v]) {
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low[u] = std::min(low[u], dfn[v]);
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}
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}
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if (dfn[u] == low[u]) {
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scc_cnt++;
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int v;
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do {
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v = st.top();
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st.pop();
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id[v] = scc_cnt;
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vis[v] = false;
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} while (v != u);
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}
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}
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int main() {
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cin >> n;
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for (int i = 1; i <= n; i++) {
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while (cin >> x, x) {
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g[i].push_back(x);
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}
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}
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for (int i = 1; i <= n; i++) {
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if (!dfn[i]) {
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tarjan(i);
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}
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}
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for (int i = 1; i <= n; i++) {
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for (int j = 0; j < g[i].size(); j++) {
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int v = g[i][j];
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if (id[i] != id[v]) {
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dout[id[i]]++;
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din[id[v]]++;
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}
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}
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}
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for (int i = 1; i <= scc_cnt; i++) {
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if (!din[i]) ans1++;
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if (!dout[i]) ans2++;
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}
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cout << ans1 << endl
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<< (scc_cnt == 1 ? 0 : std::max(ans1, ans2)) << endl;
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return 0;
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}
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