Submission #537118

#	Time	Username	Problem	Language	Result	Execution time	Memory
537118		Cantfindme	Cat in a tree (BOI17_catinatree)	C++17	100 / 100	409 ms	272560 KiB

catinatree

#include <bits/stdc++.h>
using namespace std;
#define int long long
typedef pair<int,int> pi;
#define f first
#define s second
#define FAST ios_base::sync_with_stdio(0); cin.tie(0);
#define all(x) x.begin(),x.end()

const int maxn = 200010;
const int INF = LLONG_MAX/2;
const int mod = 1e9+7;

int n, K;

//https://codeforces.com/blog/entry/70822

struct dat {
	deque <int> dp;
	dat (int v = 0) {
		dp = {v};
	}

	int size() const {
		return (int) dp.size();
	}
};
vector <int> adjlist[maxn];
vector <dat> ans;

void extend(dat &root) {
	root.dp.push_front(root.dp.front());
}

void attach(dat &a, dat &b) {
	if (a.size() < b.size()) { //b is the smaller one
		swap(a, b);
	}

	//We will at most modify the first b.dp.size values of a
	vector <int> v = vector<int>(all(b.dp));

	for (int x = 0; x < b.size(); x++) {
		int miny = max(K - x, x);
		if (miny < b.size()) {
			v[x] = max(v[x], a.dp[x] + b.dp[miny]);
		}

		if (miny < a.size()) {
			v[x] = max(v[x], b.dp[x] + a.dp[miny]);
		}
	}

	for (int i = v.size() - 1; i >= 0; i--) {
		if (i+1 < v.size()) v[i] = max(v[i], v[i+1]);
		a.dp[i] = max(a.dp[i], v[i]);
	}
}

//Return reference to dat for x
dat& dpf(int x, int p) {
	dat &res = ans[x]; //reference to thingy
	res = dat(1);

	for (auto i : adjlist[x]) if (i != p) {
		dat &u = dpf(i,x);
		extend(u);
		attach(res, u);
	}

	return res;
}

int32_t main() {
	FAST
	// ifstream cin("input.txt");

	cin >> n >> K;

	for (int i = 2; i <= n; i++) {
		int p; cin >> p;
		p++;
		adjlist[p].push_back(i);
	}

	ans.assign(n+1, {});
	cout << dpf(1, -1).dp.front();
}

Compilation message (stderr)

catinatree.cpp: In function 'void attach(dat&, dat&)':
catinatree.cpp:55:11: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   55 |   if (i+1 < v.size()) v[i] = max(v[i], v[i+1]);
      |       ~~~~^~~~~~~~~~

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