Submission #681916

#	Time	Username	Problem	Language	Result	Execution time	Memory
681916		Kahou	Cat in a tree (BOI17_catinatree)	C++14	11 / 100	9 ms	8904 KiB

catinatree

#include<bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define endl '\n'
#define mk make_pair
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

const int N = 20, M = (1<<20);
int n, d, nb[N], dp[M];
vector<int> adj[N];

void dfs(int u, int p, int t, int r) {
	if (t >= d) return;
	nb[r] ^= (1<<u);
	for (int v:adj[u]) {
		if (v == p) continue;
		dfs(v, u, t+1, r);
	}
}

void solve() {
	cin >> n >> d;
	for (int u = 1; u < n; u++) {
		int p;
		cin >> p;
		adj[u].push_back(p);
		adj[p].push_back(u);
	}
	for (int u = 0; u < n; u++) {
		dfs(u, -1, 0, u);
	}
	dp[0] = 0;
	for (int mask = 1; mask < (1<<n); mask++) {
		int u = __builtin_ctz(mask);
		dp[mask] = max(dp[mask^(1<<u)], dp[mask^(mask&nb[u])]+1);
	}
	cout << dp[(1<<n)-1] << endl;
}
int main() {
	ios::sync_with_stdio(0), cin.tie(0);
	solve();
	return 0;
}

• Subtask 1: 11 / 11
• Subtask 2: 0 / 40
• Subtask 3: 0 / 49