Fibonacci

fib2.c

#include <stdio.h>

long long fibiter(long long a,long long b,long long p,long long q,long long count){
    if(count == 0){
        return b;
    }
    if(count % 2 == 0){
        return fibiter(a,b,(p*p+q*q),(2*p*q+q*q),(count/2));
    }else{
        return fibiter((b*q+a*q+a*p),(b*p+a*q),p,q,(count-1));
    }
}

long long fib(long long n){
    return fibiter(1,0,0,1,n);
}

int main(){
    long long i;
    for(i=1;i<10;i++){
        printf("%lld\n",fib(i));
    }
    return 0;
}