Submission #1008898

#	Time	Username	Problem	Language	Result	Execution time	Memory
1008898		jer033	Detecting Molecules (IOI16_molecules)	C++17	100 / 100	39 ms	10368 KiB

molecules

#include "molecules.h"
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pli = pair<long long, int>;

std::vector<int> find_subset(int l, int u, std::vector<int> w) {
    int molecule_count = w.size();
    vector<pli> molecules;
    molecules.reserve(molecule_count);
    for (int i=0; i<molecule_count; i++)
    {
        molecules.push_back({w[i], i});
    }
    sort(molecules.begin(), molecules.end());
    ll lower_bound = l;
    ll upper_bound = u;

    vector<ll> prefix_sums;
    vector<ll> suffix_sums;
    prefix_sums.reserve(molecule_count+1);
    suffix_sums.reserve(molecule_count+1);
    prefix_sums.push_back(0);
    for (int i=0; i<molecule_count; i++)
    {
        prefix_sums.push_back(prefix_sums[i]+molecules[i].first);
    }
    suffix_sums.push_back(0);
    for (int i=0; i<molecule_count; i++)
    {
        suffix_sums.push_back(suffix_sums[i]+molecules[molecule_count-1-i].first);
    }

    int ele_count = -1;
    for (int i=0; i<=molecule_count; i++)
        if ((prefix_sums[i]<=u) and (suffix_sums[i]>=l))
            ele_count = i;
    
    if (ele_count == -1)
        return {};
    
    vector<int> rearranged_indices;
    rearranged_indices.reserve(ele_count+1);
    for (int i=0; i<ele_count; i++)
        rearranged_indices.push_back(i);
    ll curr_sum = prefix_sums[ele_count];
    int j = 0;
    while (curr_sum < l)
    {
        rearranged_indices[j] = molecule_count-1-j;
        curr_sum = curr_sum - molecules[j].first + molecules[molecule_count-1-j].first;
        j++;
    }
    
    vector<int> ans;
    ans.reserve(ele_count+1);
    for (int i=0; i<ele_count; i++)
    {
        ans.push_back(molecules[rearranged_indices[i]].second);
    }
    return ans;
}

Compilation message (stderr)

molecules.cpp: In function 'std::vector<int> find_subset(int, int, std::vector<int>)':
molecules.cpp:16:8: warning: unused variable 'lower_bound' [-Wunused-variable]
   16 |     ll lower_bound = l;
      |        ^~~~~~~~~~~
molecules.cpp:17:8: warning: unused variable 'upper_bound' [-Wunused-variable]
   17 |     ll upper_bound = u;
      |        ^~~~~~~~~~~

• Subtask 1: 9 / 9
• Subtask 2: 10 / 10
• Subtask 3: 12 / 12
• Subtask 4: 15 / 15
• Subtask 5: 23 / 23
• Subtask 6: 31 / 31