Hacktoberfestmine/Fibo_in_logN.cpp at main · pythonites/Hacktoberfestmine · GitHub

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#include<bits/stdc++.h>
#include<algorithm>
#include<unordered_map>
#include<vector>
#include<unordered_set>
#include<set>
#include<map>
#include<queue>
#include<stack>
#include<map>
using namespace std;
#define fastio() ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL)
#define MOD 1000000007
#define MOD1 998244353
#define nline "\n"
#define pb push_back
#define mp make_pair
#define ff first
#define ss second
#define PI 3.141592653589793238462
#define debug(x) cout << #x << " " << x <<endl;
#define set_bits __builtin_popcount
typedef long long ll;
typedef unsigned long long ull;
typedef long double lld;
/*---------------------------------------------------------------------------------------------------------------------------*/
ll gcd(ll a, ll b) {if (b > a) {return gcd(b, a);} if (b == 0) {return a;} return gcd(b, a % b);}
ll expo(ll a, ll b, ll mod) {ll res = 1; while (b > 0) {if (b & 1)res = (res * a) % mod; a = (a * a) % mod; b = b >> 1;} return res;}
void extendgcd(ll a, ll b, ll*v) {if (b == 0) {v[0] = 1; v[1] = 0; v[2] = a; return ;} extendgcd(b, a % b, v); ll x = v[1]; v[1] = v[0] - v[1] * (a / b); v[0] = x; return;} //pass an arry of size 3
ll mminv(ll a, ll b) {ll arr[3]; extendgcd(a, b, arr); return arr[0];} //for non prime b
ll mminvprime(ll a, ll b) {return expo(a, b - 2, b);}
bool revsort(ll a, ll b) {return a > b;}
void swap(int &x, int &y) {int temp = x; x = y; y = temp;}
ll combination(ll n, ll r, ll m, ll* fact) {ll val1 = fact[n]; ll val2 = mminvprime(fact[r], m); ll val3 = mminvprime(fact[n - r], m); return ((val1 * val2) % m * val3) % m;}
void google(int t) {cout << "Case #" << t << ": ";}
/*--------------------------------------------------------------------------------------------------------------------------*/
ll x[2][2];
void mulitply(ll a[2][2], ll b[2][2])
{
	ll c[2][2] = {{0, 0}, {0, 0}};
	for (int i = 0; i < 2; i++)
		for (int j = 0; j < 2; j++)
			for (int k = 0; k < 2; k++)
				c[i][k] = (c[i][k] + ((a[i][j] % MOD) * (b[j][k] % MOD)) % MOD) % MOD;
	x[0][0] = c[0][0];
	x[0][1] = c[0][1];
	x[1][0] = c[1][0];
	x[1][1] = c[1][1];
}
void helper(ll a[2][2], ll n)
{
	if (n == 0)
	{
		x[0][0] = 1;
		x[0][1] = 0;
		x[1][0] = 0;
		x[1][1] = 1;
		return;
	}
	helper(a, n / 2);
	mulitply(x, x);
	if (n & 1)
		mulitply(x, a);
}
int main()
{
	fastio();
#ifndef ONLINE_JUDGE
	freopen("Input.txt", "r", stdin);
	freopen("Output.txt", "w", stdout);
	freopen("Error.txt", "w", stderr);
#endif
	ll a[2][2] = {{1, 1}, {1, 0}};
	ll n;
	cin >> n;
	if (n == 0)
		cout << 0 << endl;
	else
	{
		helper(a, n - 1);
		cout << x[0][0] << endl;
	}
	return 0;
}