Submission #753567

#	Time	Username	Problem	Language	Result	Execution time	Memory
753567		rastervc	Knapsack (NOI18_knapsack)	C++17	100 / 100	105 ms	35136 KiB

knapsack

#include <algorithm>
#include <iostream>
#include <map>
#include <vector>

inline void fast_io() {
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(nullptr);
    std::cout.tie(nullptr);
}

int main() {
    fast_io();

	int limit;
	int type_num;
	std::cin >> limit >> type_num;

	std::map<int, std::vector<std::pair<int, int>>> by_weight;
	for (int t = 0; t < type_num; t++) {
		int value;
		int weight;
		int amt;
		std::cin >> value >> weight >> amt;
		if (weight <= limit && amt > 0) {
			by_weight[weight].push_back({ value, amt });
		}
	}

	std::vector<std::vector<long long>> best(by_weight.size() + 1, std::vector<long long>(limit + 1, INT32_MIN));
	best[0][0] = 0;
	int at = 1;
	for (auto &[w, items] : by_weight) {
		// sort items in reverse order by value
		std::sort(items.begin(), items.end(), std::greater<std::pair<int, int>>());
		for (int i = 0; i <= limit; i++) {
			best[at][i] = best[at - 1][i];
			int copies = 0;
			int type_at = 0;
			int curr_used = 0;
			long long profit = 0;
			
			while ((copies + 1) * w <= i && type_at < items.size()) {
				copies++;
				profit += items[type_at].first;
				if (best[at - 1][i - copies * w] != INT32_MIN) {
					best[at][i] = std::max(
					    best[at][i], best[at - 1][i - copies * w] + profit);
				}

				curr_used++;
				if (curr_used == items[type_at].second) {
					curr_used = 0;
					type_at++;
				}
			}
		}
		at++;
	}

	std::cout << *std::max_element(best.back().begin(), best.back().end());

    return 0;
}

Compilation message (stderr)

knapsack.cpp: In function 'int main()':
knapsack.cpp:43:44: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   43 |    while ((copies + 1) * w <= i && type_at < items.size()) {
      |                                    ~~~~~~~~^~~~~~~~~~~~~~

• Subtask 1: 12 / 12
• Subtask 2: 17 / 17
• Subtask 3: 20 / 20
• Subtask 4: 24 / 24
• Subtask 5: 27 / 27