Merge pull request #1555 from AlgorithmWithGod/khj20006

[20251201] BOJ / P3 / 즉흥 여행 (Hard) / 권혁준

Author: ShinHeeEul

khj20006/202512/01 BOJ P3 즉흥 여행 (Hard).md

@@ -0,0 +1,77 @@
+```cpp
+#include <bits/stdc++.h>
+using namespace std;
+
+int N, M;
+vector<vector<int>> g(200001), r(200001), v(200001);
+bitset<200001> vis;
+stack<int> st;
+int num[200001]{}, deg[200001]{}, dp[200001]{};
+
+void dfs1(int n) {
+    for(int i:g[n]) if(!vis[i]) {
+        vis[i] = 1;
+        dfs1(i);
+    }
+    st.push(n);
+}
+
+void dfs2(int n, int k) {
+    num[n] = k;
+    for(int i:r[n]) if(!vis[i]) {
+        vis[i] = 1;
+        dfs2(i, k);
+    }
+}
+
+int main(){
+	cin.tie(0)->sync_with_stdio(0);
+
+	cin>>N>>M;
+    for(int a,b;M--;) {
+        cin>>a>>b;
+        g[a].push_back(b);
+        r[b].push_back(a);
+    }
+
+    for(int i=1;i<=N;i++) if(!vis[i]) {
+        vis[i] = 1;
+        dfs1(i);
+    }
+
+    int cnt = 0;
+    vis.reset();
+    while(!st.empty()) {
+        int n = st.top(); st.pop();
+        if(vis[n]) continue;
+        vis[n] = 1;
+        dfs2(n, ++cnt);
+    }
+
+    for(int i=1;i<=N;i++) for(int j:g[i]) if(num[i] != num[j]) {
+        deg[num[i]]++;
+        v[num[j]].push_back(num[i]);
+    }
+
+    queue<int> q;
+    for(int i=1;i<=cnt;i++) if(!deg[i]) {
+        q.push(i);
+        dp[i] = 1;
+    }
+
+    while(!q.empty()) {
+        int n = q.front(); q.pop();
+        for(int i:v[n]) {
+            if(!--deg[i]) q.push(i);
+            dp[i] = max(dp[i], dp[n] + 1);
+        }
+    }
+
+    vector<int> ans;
+    for(int i=1;i<=N;i++) if(dp[num[i]] == cnt) ans.push_back(i);
+
+    cout<<ans.size()<<'\n';
+    for(int i:ans) cout<<i<<' ';
+
+}
+```