Submission #1250054

#	Time	Username	Problem	Language	Result	Execution time	Memory
1250054		testacc11	Triple Peaks (IOI25_triples)	C++20	Compilation error	0 ms	0 KiB

triples

#include <bits/stdc++.h>
using namespace std;
using ll = long long;

ll count_triples(const vector<int>& H) {
    int N = H.size();
    // L1[j] = list of all i<j with H[i] = j-i
    vector<vector<int>> L1(N);
    // S[T] = list of all k with k+H[k] = T
    vector<vector<int>> S(2*N);
    for(int i = 0; i < N; i++) {
        int j1 = i + H[i];
        if(j1 < N) L1[j1].push_back(i);
        int T = i + H[i];
        S[T].push_back(i);
    }

    ll ans = 0;
    for(int j = 0; j < N; j++) {
        int hj = H[j];
        // Case A: H[j] = d1 = j-i
        {
            int i = j - hj;
            if(i >= 0) {
                int hi = H[i];
                int k = j + hi;
                if(k < N && hi + hj == H[k]) {
                    ans++;
                }
            }
        }
        // Case B: H[j] = d2 = k-j
        {
            int k = j + hj;
            if(k < N) {
                int hk = H[k];
                int i = k - hk;
                if(i >= 0 && i < j && hk - hj == H[i]) {
                    ans++;
                }
            }
        }
        // Case C1: H[j] = d3, with H[i]=d1 and H[k]=d2
        for(int i : L1[j]) {
            int hi = H[i];
            int k = i + hj;
            if(k > j && k < N && H[k] == hj - hi) {
                ans++;
            }
        }
        // Case C2: H[j] = d3, with H[k]=d1 and H[i]=d2
        int Tj = j + hj;
        if(Tj < (int)S.size()) {
            for(int k : S[Tj]) {
                if(k <= j) continue;
                int i = k - hj;
                if(i >= 0 && i < j && H[i] == k - j) {
                    ans++;
                }
            }
        }
    }
    return ans;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int part;
    cin >> part;
    if(part != 1) return 0;  // only Part I

    int N;
    cin >> N;
    vector<int> H(N);
    for(int i = 0; i < N; i++) {
        cin >> H[i];
    }

    ll result = count_triples(H);
    cout << result << "\n";
    return 0;
}

Compilation message (stderr)

/usr/bin/ld: /tmp/cc3kPgfd.o: in function `main':
grader.cpp:(.text.startup+0x0): multiple definition of `main'; /tmp/cclxRyiv.o:triples.cpp:(.text.startup+0x0): first defined here
/usr/bin/ld: /tmp/cc3kPgfd.o: in function `main':
grader.cpp:(.text.startup+0x18a): undefined reference to `construct_range(int, int)'
/usr/bin/ld: grader.cpp:(.text.startup+0x37b): undefined reference to `count_triples(std::vector<int, std::allocator<int> >)'
collect2: error: ld returned 1 exit status