Factorial, Fibonacci Recursion

factorial (tail Recursion)

int Factorial(int n, int memo) {
    if(n<=1) return memo;
    return Factorial(n-1, n*memo);
}

fibonacci (memoization)

int Fib(int n) {
    if(n<=1) 
    	return n;
    if(F[n] != 0)
    	return F[n];
    F[n] = Fib(n-1) + Fib(n-2);
    return F[n];    
}