Submission #824306

#	Time	Username	Problem	Language	Result	Execution time	Memory
824306		NK_	Magic Tree (CEOI19_magictree)	C++17	20 / 100	118 ms	22532 KiB

magictree

// Success consists of going from failure to failure without loss of enthusiasm
#include <bits/stdc++.h>

using namespace std;

#define nl '\n'
#define pb push_back 
#define mp make_pair
#define f first
#define s second
#define sz(x) int(x.size())

template<class T> using V = vector<T>;
using vi = V<int>;
using pi = pair<int, int>;
using ll = long long;
using vl = V<ll>;

struct Seg {
	const ll ID = 0, IDL = -1; ll comb(ll a, ll b) { return max(a, b); }
	int n; vl seg, lazy; void init(int _n) {
		n = 1; while(n < _n) n *= 2; 
		seg.assign(2 * n, ID); lazy.assign(2 * n, IDL);
	}
	void pull(int x) { seg[x] = comb(seg[2*x], seg[2*x+1]); }
	void push(int x, int L, int R) {
		if (lazy[x] != IDL) {
			seg[x] = lazy[x];
			if (L != R) for(int i = 0; i < 2; i++) lazy[2*x+i] = lazy[x];
			lazy[x] = IDL;
		}
	}

	void upd(int l, int r, ll v, int x, int L, int R) {
		push(x, L, R); if (r < L || R < l) return;
		if (l <= L && R <= r) {
			lazy[x] = v; push(x, L, R); return;
		}

		int M = (L + R) / 2;
		upd(l, r, v, 2 * x, L, M);
		upd(l, r, v, 2 * x + 1, M + 1, R);
		pull(x);
	}

	ll query(int l, int r, int x, int L, int R) {
		push(x, L, R); if (r < L || R < l) return ID;
		if (l <= L && R <= r) return seg[x];

		int M = (L + R) / 2;
		return comb(
			query(l, r, 2 * x, L, M), 
			query(l, r, 2 * x + 1, M + 1, R)
		);
	}

	void upd(int l, int r, ll v) { upd(l, r, v, 1, 0, n - 1); }
	ll query(int l, int r) { return query(l, r, 1, 0, n - 1); }
};

int main() {
	cin.tie(0)->sync_with_stdio(0);
	
	int N, M, K; cin >> N >> M >> K; 

	// (euler tour + segment tree + offline queries)? to compute dp
	// then basic tree dp with dp values to get answer

	V<vi> chd(N); for(int u = 1; u < N; u++) {
		int p; cin >> p; --p;
		chd[p].pb(u);
	}

	vi st(N), en(N); int t = 0;
	function<void(int)> gen = [&](int u) {
		st[u] = t++;
		for(auto& v : chd[u]) gen(v);
		en[u] = t-1;
	};

	gen(0);

	V<array<int, 3>> E;
	for(int i = 0; i < M; i++) {
		int v, d, w; cin >> v >> d >> w; --v, --d;
		E.push_back({d, v, w});
	}

	sort(begin(E), end(E), [&](array<int, 3> x, array<int, 3> y) {
		if (x[0] == y[0]) return st[x[1]] > st[y[1]];
		return x[0] < y[0];
	});

	Seg T; T.init(N);
	vl dp(N, 0);

	for(auto q : E) {
		auto [d, u, w] = q;
		// cout << d << " " << u << endl;

		dp[u] = w;
		for(auto& v : chd[u]) {
			// cout << v << endl;
			// cout << st[v] << " " << en[v] << endl;
			// cout << T.query(st[v], en[v]) << endl;
			// cout << endl;
			dp[u] += T.query(st[v], en[v]);
		}
		// T.upd(st[u] + 1, en[u], 0);
		T.upd(st[u], st[u], dp[u]);
		// cout << u << " - " << dp[u] << endl;
	}

	function<ll(int)> ans = [&](int u) {
		ll best = 0;
		for(auto& v : chd[u]) best += ans(v);
		return max(best, dp[u]);
	};

	cout << ans(0) << nl;

    return 0;
}			

• Subtask 1: 6 / 6
• Subtask 2: 3 / 3
• Subtask 3: 11 / 11
• Subtask 4: 0 / 12
• Subtask 5: 0 / 16
• Subtask 6: 0 / 13
• Subtask 7: 0 / 22
• Subtask 8: 0 / 17