Submission #1127390

#	Time	Username	Problem	Language	Result	Execution time	Memory
1127390		kh0i	Cat in a tree (BOI17_catinatree)	C++20	100 / 100	75 ms	28484 KiB

catinatree

#include "bits/stdc++.h"
using namespace std;

#ifdef LOCAL
#include "debug.h"
#else
#define debug(...)
#endif

using ll = long long;
using pii = pair<int, int>;

#define F first
#define S second
#define sz(x) (int)((x).size())
#define all(x) (x).begin(), (x).end()

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll get_rand(ll l, ll r) {
    assert(l <= r);
    return uniform_int_distribution<ll> (l, r)(rng);
}

struct Deque{
    vector<int> a;
    int size(){ return sz(a); }
    void push_front(int x){
        a.push_back(x);
    }
    int& operator [] (int x){
        return a.rbegin()[x];
    }
    void clear(){
        vector<int>().swap(a);
    }
};

const int N = 2e5 + 3;

int n, d;
vector<int> g[N];
Deque f[N];

void dfs(int u){
    f[u].push_front(1);
    for(int v : g[u]){
        dfs(v);
        f[v].push_front(f[v][0]);
        if(sz(f[v]) > sz(f[u]))
            swap(f[u], f[v]);
        for(int i = 0; i < sz(f[v]); ++i){
            int t = max(i, d - i);
            int fi = (t < sz(f[v]) ? f[v][t] + f[u][i] : f[u][i]);
            int se = (t < sz(f[u]) ? f[u][t] + f[v][i] : f[u][i]);
            f[u][i] = max(fi, se);
        }
        for(int i = sz(f[v]) - 1; i >= 0; --i){
            if(i + 1 < sz(f[u]))
                f[u][i] = max(f[u][i], f[u][i + 1]);
        }
        f[v].clear();
    }
}

void solve(){
    cin >> n >> d;
    for(int i = 1; i < n; ++i){
        int p;
        cin >> p;
        g[p].push_back(i);
    }
    dfs(0);
    cout << f[0][0];
}

int32_t main() {
    cin.tie(nullptr)->sync_with_stdio(0);
    #define task "troll"
    if(fopen(task".inp", "r")){
        freopen(task".inp", "r", stdin);
        freopen(task".out", "w", stdout);
    }
    int test = 1;
//    cin >> test;
    for(int i = 1; i <= test; ++i){
//        cout << "Case #" << i << ": ";
        solve();
    }
    #ifdef LOCAL
        cerr << "\n[Time]: " << 1000.0 * clock() / CLOCKS_PER_SEC << " ms.\n";
    #endif
    return 0;
}

Compilation message (stderr)

catinatree.cpp: In function 'int32_t main()':
catinatree.cpp:80:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   80 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
catinatree.cpp:81:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   81 |         freopen(task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 11 / 11
• Subtask 2: 40 / 40
• Subtask 3: 49 / 49