Cod sursa(job #1925435)

Utilizator Alexa2001Alexa Tudose Alexa2001 Data 13 martie 2017 10:35:42
Problema Al k-lea termen Fibonacci Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.07 kb
#include <fstream>

using namespace std;

ifstream fin("kfib.in");
ofstream fout("kfib.out");

const int Mod = 666013;
int ans[2][2], m[2][2], n;

void inm(int a[2][2], int b[2][2]) /// inmultesc a si b, iar rezultatul il pun in a
{
    int i, j, k;
    long long c[2][2];

    for(i=0; i<2; ++i)
        for(j=0; j<2; ++j)
        {
            c[i][j] = 0;
            for(k=0; k<2; ++k)
                c[i][j] += 1LL * a[i][k] * b[k][j];
        }

    for(i=0; i<2; ++i)
        for(j=0; j<2; ++j)
            a[i][j] = (int)(c[i][j] % Mod);
}

void power(int k)
{
    if(!k) return;
    if(k%2==1) inm(ans, m); /// exponentul e impar, deci inmultesc rezultatul cu m
    inm(m, m);  /// ridic m la patrat
    power(k/2); /// calculez (m^2)^(k/2)
}

int main()
{
    fin >> n;

    m[0][0] = 0; m[0][1] = m[1][0] = m[1][1] = 1; /// initializez m
    ans[0][0] = ans[0][1] = 1; ans[1][0] = ans[1][1] = 0; /// initializez ans cu matricea ce reprezinta primii doi termeni ai sirului

    power(n-1);
    fout << ans[0][0] << '\n';

    return 0;
}