[20251120] BOJ / P5 / Domain clusters / 권혁준

khj20006/202511/20 BOJ P5 Domain clusters.md

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+```cpp
+#include <bits/stdc++.h>
+using namespace std;
+
+int D, L;
+vector<vector<int>> v(5001), r(5001);
+
+bitset<5001> vis;
+int cnt = 0, ans = 0;
+stack<int> st;
+
+void dfs1(int n) {
+    for(int i:v[n]) if(!vis[i]) {
+        vis[i] = 1;
+        dfs1(i);
+    }
+    st.push(n);
+}
+
+void dfs2(int n) {
+    cnt++;
+    for(int i:r[n]) if(!vis[i]) {
+        vis[i] = 1;
+        dfs2(i);
+    }
+}
+
+int main(){
+    cin.tie(0)->sync_with_stdio(0);
+
+    for(cin>>D>>L;L--;) {
+        int a,b;
+        cin>>a>>b;
+        v[a].push_back(b);
+        r[b].push_back(a);
+    }
+
+    for(int i=1;i<=D;i++) if(!vis[i]) {
+        vis[i] = 1;
+        dfs1(i);
+    }
+    vis.reset();
+    while(!st.empty()) {
+        int n = st.top(); st.pop();
+        if(vis[n]) continue;
+        cnt = 0;
+        vis[n] = 1;
+        dfs2(n);
+        ans = max(ans, cnt);
+    }
+
+    cout<<ans;
+
+}
+```