Submission #1062774

#	Time	Username	Problem	Language	Result	Execution time	Memory
1062774		vuavisao	Jobs (BOI24_jobs)	C++17	40 / 100	91 ms	33732 KiB

Main

#include <bits/stdc++.h>
#pragma GCC optimize("O3", "unroll-loops")
using namespace std;

using ll = long long;

const int N = 300'000 + 10;
const ll INF = 1'000'000'000'000'000'000;

int n;
ll s;

vector<int> g[N];
ll cost[N];
int parent[N];

namespace sub1 {
	bool check() {
		return (s == INF);
	}

	ll dp[N];

	void dfs(int u) {
		dp[u] = cost[u];
		for (const auto& v : g[u]) {
			dfs(v);
			dp[u] += dp[v];
		}
		dp[u] = max(dp[u], 0ll);
	}


	void solve() {
		dfs(0);
		// for (int u = 1; u <= n; ++ u) cout << dp[u] << " \n"[u == n];
		cout << dp[0];
	}
}

namespace sub23 {
	bool check() {
		for (int u = 1; u <= n; ++ u) {
			if (parent[u] != 0 && parent[u] != u - 1) return false;
		}
		return true;
	}
	
	ll sum[N], mi[N];

	void solve() {
		ll first = s;
		vector<pair<ll, ll>> candidates;
		mi[0] = INF;
		for (int u = 1; u <= n; ++ u) {
			int p = parent[u];
			ll add = sum[p] + cost[u];
			mi[u] = min(mi[p], add);
			if (add > 0) {
				candidates.push_back(make_pair(-mi[u], add));
				sum[u] = 0;
			}
			else {
				sum[u] = add;
			}
		}
		sort(candidates.begin(), candidates.end());
		for (const auto& [need, add] : candidates) {
			if (s - need < 0) {
				break;
			}
			s += add;
		}
		cout << s - first;
	}
}

namespace sub4 {
	bool check() {
		return (n <= 2'000);
	}

	ll mi[N], sum[N];

	void dfsRem(int u, int& best) {
		int p = parent[u];
		ll add = sum[p] + cost[u];
		mi[u] = min(mi[p], add);
		if (add > 0) {
			if (best == -1 || mi[u] > mi[best]) {
				best = u;
			}
			return;
		}
		for (const auto& v : g[u]) {
			dfsRem(v, best);
		}
	}

	void solve() {
		ll first = s;
		for (int cnt = 1; cnt <= 2'000; ++ cnt) {
			int best = -1;
			for (int u = 0; u <= n; ++ u) {
				mi[u] = INF;
				sum[u] = 0;
			}
			dfsRem(0, best);
			if (best == -1 || -mi[best] > s) {
				break;
			}
			ll ss = 0;
			while (best != 0) {
				ss += cost[best];
				cost[best] = 0;
				best = parent[best];
			}
			s += ss;
		}
		cout << s - first;
	}
}

int32_t main() {
	std::ios_base::sync_with_stdio(false);
	std::cin.tie(nullptr); std::cout.tie(nullptr);
	cin >> n >> s;
	for (int u = 1; u <= n; ++ u) {
		cin >> cost[u] >> parent[u];
		g[parent[u]].push_back(u);
	}
	if (sub1::check()) {
		sub1::solve();
		return 0;
	}
	if (sub23::check()) {
		sub23::solve();
		return 0;
	}
	if (sub4::check()) {
		sub4::solve();
		return 0;
	}
	assert(false);
	return (0 ^ 0);
}

/// Code by vuavisao

• Subtask 1: 11 / 11
• Subtask 2: 14 / 14
• Subtask 3: 15 / 15
• Subtask 4: 0 / 29
• Subtask 5: 0 / 31