Submission #1290819

#	Time	Username	Problem	Language	Result	Execution time	Memory
1290819		ecen30	Triple Peaks (IOI25_triples)	C++20	Compilation error	0 ms	0 KiB

triples

//testing AI code
#include <vector>
#include <unordered_map>
#include <algorithm>

long long count_triples(const std::vector<int>& H) {
    long long result = 0;
    int N = H.size();
    std::unordered_map<int, std::vector<int>> positions;

    // Precompute for each valid height, all positions where it appears
    for (int idx = 0; idx < N; ++idx)
        positions[H[idx]].push_back(idx);

    // For every possible pair (i, k), try to find j in between such that
    // the triple satisfies the condition
    for (int i = 0; i < N; ++i) {
        for (int k = i + 2; k < N; ++k) {
            int d2 = k - i;  // distance from i to k
            int h1 = H[i], h3 = H[k];

            // The only possible j must be i < j < k
            // The distances between the three indices are: j-i, k-i, k-j
            // so the triple of distances (d1, d2, d3) where:
            //  d1 = j-i
            //  d2 = k-i
            //  d3 = k-j = k-i - (j-i)
            // Thus for a given (i, k), we want to pick j so that the heights H[i], H[j], H[k]
            // are a permutation of (j-i, k-i, k-j)

            // For all possible j between i+1 and k-1
            for (int j = i + 1; j < k; ++j) {
                std::vector<int> dists = {j - i, k - i, k - j};
                std::vector<int> heights = {H[i], H[j], H[k]};
                std::sort(dists.begin(), dists.end());
                std::sort(heights.begin(), heights.end());
                if (dists == heights)
                    result++;
            }
        }
    }
    return result;
}

Compilation message (stderr)

/usr/bin/ld: /tmp/cccmTrkh.o: in function `main':
grader.cpp:(.text.startup+0x197): undefined reference to `construct_range(int, int)'
/usr/bin/ld: grader.cpp:(.text.startup+0x367): undefined reference to `count_triples(std::vector<int, std::allocator<int> >)'
collect2: error: ld returned 1 exit status