Submission #1189243

#	Time	Username	Problem	Language	Result	Execution time	Memory
1189243		Zakir060	Detecting Molecules (IOI16_molecules)	C++20	Compilation error	0 ms	0 KiB

molecules

// Likely contents of your submission file (e.g., molecules.cpp)

#include <vector>
#include <numeric>
#include <algorithm>
#include <utility> // For std::pair

// Structure to store molecule weight along with its original index
struct Molecule {
    long long weight; // Use long long for weight and sums
    int index;        // Original index (0 to n-1)
};

// Custom comparison function for sorting Molecules in descending order of weight
bool compareMoleculesDesc(const Molecule& a, const Molecule& b) {
    if (a.weight != b.weight) {
        return a.weight > b.weight;
    }
    // Consistent tie-breaking (optional but good practice)
    return a.index < b.index;
}

/**
 * @brief Finds a subset of molecules whose total weight falls within the range [l, u].
 */
std::vector<int> find_subset(int l_int, int u_int, const std::vector<int>& w) {
    long long l = l_int;
    long long u = u_int;
    int n = w.size();

    std::vector<Molecule> molecules_to_consider;
    molecules_to_consider.reserve(n);

    // 1. Filter and Check Single Element Solution
    for (int i = 0; i < n; ++i) {
        long long current_weight = w[i];
        if (current_weight >= l && current_weight <= u) {
            return {i};
        }
        // Only consider molecules with weight <= u for potential combination
        if (current_weight <= u) {
             molecules_to_consider.push_back({current_weight, i});
        }
    }

    // 2. Sort candidates in descending order by weight
    std::sort(molecules_to_consider.begin(), molecules_to_consider.end(), compareMoleculesDesc);

    long long current_sum = 0;
    std::vector<int> current_subset_indices;
    current_subset_indices.reserve(molecules_to_consider.size());

    // 3. Greedy Selection (Descending): Add if sum does not exceed u
    for (const auto& mol : molecules_to_consider) {
        if (current_sum + mol.weight <= u) {
            current_sum += mol.weight;
            current_subset_indices.push_back(mol.index);
        }
    }

    // 4. Final Check: After considering all candidates, check if the resulting sum is >= l
    if (current_sum >= l) {
        return current_subset_indices;
    } else {
        return {}; // Return empty vector
    }
}

// --- NO C Interface Wrapper needed if the grader calls the C++ function ---

Compilation message (stderr)

molecules.h:1:9: warning: #pragma once in main file
    1 | #pragma once
      |         ^~~~
molecules_c.h:1:9: warning: #pragma once in main file
    1 | #pragma once
      |         ^~~~
/usr/bin/ld: /tmp/ccuB1v7B.o: in function `main':
grader.cpp:(.text.startup+0x173): undefined reference to `find_subset(int, int, std::vector<int, std::allocator<int> >)'
collect2: error: ld returned 1 exit status