[C/C++]Fibonacci numbers

　　

int fib(int n){
    if (n ==1|| n ==2) {
        return1;
    }
    return fib(n-1) + fib(n-2);
}

　　

void fib_(int n, int* fibn, int* fibn_1){
    if (n ==2|| n ==1) {
        *fibn =1;
        *fibn_1 =1;
    }
    else{
        fib_(n-1,fibn,fibn_1);
        *fibn =*fibn +*fibn_1;
        *fibn_1 =*fibn -*fibn_1;
    }
};

int fib2(int n ){
    int fibn;
    int fib_1;
    fib_(n,&fibn,&fib_1);
    return fibn;
}

 

 

int fib_tail_recur_(int n,int fib_n, int fib_n_minus1)
{
    if(n == 3)
    {
        return fib_n + fib_n_minus1;
    }
    else
    {
        return fib_tail_recur_(n-1,fib_n + fib_n_minus1, fib_n);
    }
}

int fib_tail_recur(int n)
{
    if (n < 3){
        return 1;
    }else
    {
        return fib_tail_recur_(n,1,1);
    }
}