Resuelve https://omegaup.com/arena/problem/siteda

siteda.cpp

#include <bits/stdc++.h>
using std::vector;

bool cycleIsIncomplete(vector<int> const & sequence, int a, int b, int idx) {
    unsigned m = sequence.size();
    int aa = sequence[(idx-2+m)%m];
    int bb = sequence[(idx-1+m)%m];
    return aa != a || bb != b;
}

int main() {
    int a, b;
    std::cin >> a >> b;
    vector<int> sequence{a, b, 0};
    int count = 0;
    unsigned idx = 2;
    std::cout << a << " " << b << " ";
    unsigned m = sequence.size();
    do {
        int x = sequence[(idx-2+m)%m];
        int y = sequence[(idx-1+m)%m];
        sequence[idx] = (x + y) % 10;
        std::cout << sequence[idx] << " ";
        idx = (idx + 1) % m;
        count++;
    } while (cycleIsIncomplete(sequence, a, b, idx));
    std::cout << "\n" <<  count << "\n";
    return EXIT_SUCCESS;
}