Cod sursa(job #3276777)

Utilizator alexsimedreaAlexandru Simedrea alexsimedrea Data 14 februarie 2025 17:38:40
Problema Al k-lea termen Fibonacci Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 1.39 kb
#include <fstream>
#include <iostream>
#include <vector>

constexpr int MOD = 666013;

std::vector<std::vector<long long>> multiply(const std::vector<std::vector<long long>> &a,
                                             const std::vector<std::vector<long long>> &b) {
    std::vector<std::vector<long long>> result(2, std::vector<long long>(2, 0));
    for (int i = 0; i < 2; ++i) {
        for (int j = 0; j < 2; ++j) {
            for (int k = 0; k < 2; ++k) {
                result[i][j] = (result[i][j] + a[i][k] * b[k][j]) % MOD;
            }
        }
    }
    return result;
}

std::vector<std::vector<long long>> matrixPower(std::vector<std::vector<long long>> base, long long exp) {
    std::vector<std::vector<long long>> result = {{1, 0}, {0, 1}};
    while (exp > 0) {
        if (exp % 2 == 1) {
            result = multiply(result, base);
        }
        base = multiply(base, base);
        exp /= 2;
    }
    return result;
}

long long fibonacci(long long k) {
    if (k == 0)
        return 0;
    if (k == 1)
        return 1;
    std::vector<std::vector<long long>> base = {{0, 1}, {1, 1}};
    std::vector<std::vector<long long>> result = matrixPower(base, k - 1);
    return result[1][1];
}

int main() {
    std::ifstream fin("kfib.in");
    std::ofstream fout("kfib.out");

    long long k;
    fin >> k;

    long long result = fibonacci(k);
    fout << result << std::endl;

    return 0;
}