Submission #1018388

#	Time	Username	Problem	Language	Result	Execution time	Memory
1018388		Owstin	Knapsack (NOI18_knapsack)	C++14	100 / 100	107 ms	35240 KiB

knapsack

#include <algorithm>

#include <iostream>

#include <map>

#include <vector>


using std::cout;

using std::endl;

using std::pair;

using std::vector;


int main() {

	int limit;

	int type_num;

	std::cin >> limit >> type_num;


	std::map<int, vector<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});

		}

	}


	/*

	 * best[i][j] contains the most value we can

	 * get using j weight and the first i weight types

	 */

	vector<vector<long long>> best(by_weight.size() + 1,

	                               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<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;

			// go through as many items until we run out of items or usable

			// weight

			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++;

	}

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

}

Compilation message (stderr)

knapsack.cpp: In function 'int main()':
knapsack.cpp:65:13: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   65 |  for (auto &[w, items] : by_weight) {
      |             ^
knapsack.cpp:87:44: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   87 |    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