Submission #1319369

#	Time	Username	Problem	Language	Result	Execution time	Memory
1319369		conthoanco	Knapsack (NOI18_knapsack)	C++20	49 / 100	15 ms	540 KiB

knapsack

#include <bits/stdc++.h>
using namespace std;
const long long INF = 1e16;
const int S = 2005;

int s, n;
vector<pair<int,int>> group[S], sum_group[S];
long long dp[S];
void input()
{
    cin >> s >> n;
    for(int i = 1; i <= n; ++i) {
        int v, w, k;
        cin >> v >> w >> k;
        group[w].push_back({v, k});
    }
}

long long get_val(int w, int t)
{
    if(sum_group[w].size() == 0) return -1;
    if(sum_group[w].back().second < t) return -1;

    int low = 0, high = sum_group[w].size() - 1, pos = high;
    while(low <= high) {
        int mid = (low + high) / 2;
        if(sum_group[w][mid].second >= t) {
            pos = mid;
            high = mid - 1;
        }
        else {
            low = mid + 1;
        }
    }

    long long ans = 0;
    if(pos > 0) {
        ans += sum_group[w][pos - 1].first;
        t -= sum_group[w][pos - 1].second;
    }

    ans += 1ll * group[w][pos].first * t;

    return ans;
}

void solve()
{
    for(int w = 1; w <= s; ++w) {
        sort(group[w].begin(), group[w].end(), greater<pair<long long,long long>>());

        long long sum_v = 0, sum_k = 0;
        for(int i = 0; i < group[w].size(); ++i) {
            sum_v += 1ll * group[w][i].first * group[w][i].second;
            sum_k += 1ll * group[w][i].second;

            sum_group[w].push_back({sum_v, sum_k});
        }
    }

    long long ans = 0;
    for(int x = 1; x <= s; ++x) dp[x] = -INF;
    dp[0] = 0;

    for(int w = 1; w <= s; ++w) {
        for(int x = s; x >= w; --x) {
            for(int t = 1; t <= x / w; ++t) {
                int old_x = x - w * t;
                if(dp[old_x] == -INF) continue;

                long long val = get_val(w, t);
                if(val == -1) break;

//                cerr << x << ' ' << w << ' ' << t << ' ' << val << endl;

                dp[x] = max(dp[x], dp[old_x] + val);
            }
        }
    }

    cout << *max_element(dp, dp + s + 1);
}

int main()
{
    if(fopen("trash.inp" , "r"))
        freopen("trash.inp" , "r" , stdin) , freopen("trash.out" , "w" , stdout);
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    input();
    solve();
}

Compilation message (stderr)

knapsack.cpp: In function 'int main()':
knapsack.cpp:87:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   87 |         freopen("trash.inp" , "r" , stdin) , freopen("trash.out" , "w" , stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
knapsack.cpp:87:53: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   87 |         freopen("trash.inp" , "r" , stdin) , freopen("trash.out" , "w" , stdout);
      |                                              ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 12 / 12
• Subtask 2: 17 / 17
• Subtask 3: 20 / 20
• Subtask 4: 0 / 24
• Subtask 5: 0 / 27