Submission #1256988

#	Time	Username	Problem	Language	Result	Execution time	Memory
1256988		cjspd_oly	Knapsack (NOI18_knapsack)	C++17	100 / 100	61 ms	33096 KiB

knapsack

#include <bits/stdc++.h>

using namespace std;

using ll = long long;
using ld = long double;
using vi = vector<int>;
using vvi = vector<vi>;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vii = vector<pii>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vllll = vector<pll>;

#define pb push_back
#define eb emplace_back
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define sz(x) (int)(x).size()

void setIO(string name = "")
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    if (!name.empty())
    {
        (void)freopen((name + ".in").c_str(), "r", stdin);
        (void)freopen((name + ".out").c_str(), "w", stdout);
    }
}

const ld pi = 3.14159265358979323846;

const ll LINF = 1e18;
const ll INF = 1e9;

const ll MOD = 1e9 + 7;
// const ll MOD = 998244353;

const ll MAXN = 2e5 + 5;

void solve()
{
    int S, N;
    cin >> S >> N;
    map<int, vii> by_weight;
    for (int i = 0; i < N; i++)
    {
        int value, weight, qty;
        cin >> value >> weight >> qty;
        if (weight <= S && qty > 0)
            by_weight[weight].pb({value, qty});
    }

    vvll best(by_weight.size() + 1, vll(S + 1, -1));
    best[0][0] = 0;
    int at = 1; // best[?][]; at represent `?` which group of weight, like a coordinate compression; 1-based indexing

    for (auto &[w, items] : by_weight)
    {
        sort(all(items), greater<pii>());
        for (int i = 0; i <= S; ++i)
        {
            best[at][i] = best[at - 1][i];
            int copies = 0, type_at = 0, curr_used = 0;
            ll profit = 0;
            while ((copies + 1) * w <= i && type_at < items.size())
            {
                ++copies;
                profit += items[type_at].first;
                // if (best[at - 1][i - copies * w] != -1)
                    best[at][i] = 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(all(best.back()));
}

int main()
{
    setIO("");

    int t = 1;
    // cin >> t;
    while (t--)
        solve();

    return 0;
}

Compilation message (stderr)

knapsack.cpp: In function 'void setIO(std::string)':
knapsack.cpp:28:22: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   28 |         (void)freopen((name + ".in").c_str(), "r", stdin);
      |               ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
knapsack.cpp:29:22: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   29 |         (void)freopen((name + ".out").c_str(), "w", stdout);
      |               ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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