#include <bits/stdc++.h> using namespace std; #define int long long #define FOR(I, L, R) for(int I(L) ; I <= (int)R ; ++I) #define FOD(I, R, L) for(int I(R) ; I >= (int)L ; --I) #define FOA(I, A) for(auto &I : A) #define print(A,L,R) FOR(OK, L, R){if(A[OK]<=-oo / 10||A[OK]>=oo)cout<<"- ";else cout<<A[OK]<<' ';}cout<<'\n'; #define prints(A) FOA(OK, A){cout<<OK<<' ';}cout << '\n'; #define printz(A,L,R) FOR(OK, 0, L){FOR(KO, 0, R){if(A[OK][KO]>-oo&&A[OK][KO]<oo)cout<<A[OK][KO]<<' ';else cout << "- ";} cout << '\n';}cout << '\n'; #define fs first #define sd second #define ii pair<int,int> #define iii pair<int, ii> #define all(A) A.begin(), A.end() #define quickly ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0); #define FILE "catinatree" #define pow ladsf const int N = 2e5 + 5; const int SQRT = 450; const int mod = 1e9 + 7; const int oo = 1e18; int n, k; vector<int> g[N]; namespace LessSQRT{ static int dp[N][SQRT + 5]; static int pre[N][SQRT + 5], h[N]; static int f[SQRT + 5]; void DFS(int u, int par){ FOA(v, g[u]){ if(v == par){ continue; } DFS(v, u); h[u] = max(h[u], h[v] + 1); } FOR(i, 0, min(k + 1, h[u])){ f[i] = 0; FOA(v, g[u]){ if(v == par){ continue; } f[i] += pre[v][max({0LL, i - 1, k - i})]; } } dp[u][0] = f[0] + 1; FOA(v, g[u]){ if(v == par){ continue; } FOR(i, 1, min(k, h[u])){ dp[u][i] = max(dp[u][i], f[i] + dp[v][i - 1] - pre[v][max({0LL, i - 1, k - i})]); } } if(h[u] > k) dp[u][k + 1] = f[k + 1]; FOD(i, min(k + 1, h[u]), 0){ pre[u][i] = max(dp[u][i], pre[u][i + 1]); } } void solve(){ DFS(0, -1); cout << pre[0][0]; } } namespace MoreSQRT{ static vector<int> dp[N]; static int sz[N]; static int LIMIT; void DFS(int u, int par){ sz[u] = 1; dp[u].assign(2, -oo); dp[u][0] = oo; dp[u][1] = 0; FOA(v, g[u]){ if(v == par){ continue; } DFS(v, u); int a = (int)dp[u].size() - 1; int b = (int)dp[v].size() - 1; int newSz = min(LIMIT, a + b); vector<int> nxt(newSz + 1, -oo); // trường hợp không lấy gì từ v: sao chép dp[u] for(int i = 0; i <= a && i <= newSz; ++i){ nxt[i] = max(nxt[i], dp[u][i]); } // kết hợp: lấy j >= 1 từ v (j = 0 đã xử lý ở trên) for(int i = 0; i <= a; ++i){ if(dp[u][i] <= -oo/4) continue; for(int j = 1; j <= b && i + j <= newSz; ++j){ if(dp[v][j] <= -oo/4) continue; if(dp[u][i] + dp[v][j] + 1 > k){ int val = (int)min(dp[u][i], dp[v][j] + 1); nxt[i + j] = max(nxt[i + j], val); } // nếu điều kiện không thỏa, trạng thái i (không thêm j) đã được giữ } } dp[u].swap(nxt); sz[u] = (int)dp[u].size() - 1; } } void solve(){ LIMIT = max(1LL, n / (k + 1) + 1); DFS(0, -1); for(int i = sz[0]; i >= 0; --i){ if(dp[0][i] >= 0){ cout << i; return; } } cout << 0; } } signed main(){ quickly if(fopen(FILE".inp", "r")){ freopen(FILE".inp", "r", stdin); freopen(FILE".out", "w", stdout); } cin >> n >> k; --k; FOR(v, 1, n - 1){ int u; cin >> u; g[u].push_back(v); g[v].push_back(u); } if(k < SQRT){ LessSQRT::solve(); } else{ MoreSQRT::solve(); } }

catinatree.cpp: In function 'int main()':
catinatree.cpp:145:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  145 |                 freopen(FILE".inp", "r", stdin);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
catinatree.cpp:146:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  146 |                 freopen(FILE".out", "w", stdout);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~