[20251108] BOJ / P5 / 나는 뱀파이어 / 권혁준

Author: oncsr

khj20006/202511/08 BOJ P5 나는 뱀파이어.md

@@ -0,0 +1,40 @@
+```cpp
+#include <bits/stdc++.h>
+using namespace std;
+
+int N, M, R;
+vector<vector<int>> v(100001);
+
+pair<int, int> f(int n, int p, int t) {
+    int d = t, c = 0, l = 0;
+    for(int i:v[n]) if(i != p) {
+        auto [dd, cc] = f(i, n, t);
+        d = min(d, dd+1);
+        c += cc;
+        l++;
+    }
+    if(!l) return {0,1};
+    if(d == t && n != R) c++, d = 0;
+    return {d,c};
+}
+
+int main() {
+    cin.tie(0)->sync_with_stdio(0);
+
+    cin>>N>>M>>R;
+    for(int i=1,a,b;i<N;i++) {
+        cin>>a>>b;
+        v[a].push_back(b);
+        v[b].push_back(a);
+    }
+
+    int s = 1, e = N, m = (s+e)>>1;
+    while(s<e) {
+        if(f(R, 0, m).second > M) s = m+1;
+        else e = m;
+        m = (s+e)>>1;
+    }
+    cout<<(m == N ? -1 : m);
+
+}
+```