Fibonacci

1) Non-recursive:

　　

class Solution {
    /**
     * @param n: an integer
     * @return an integer f(n)
     */
    public int fibonacci(int n) {
        // write your code here
        int n1 = 0;
        int n2 = 1;
        int n3 = 1; //n1+n2
        if(n == 1){
            return n1;
        } else if (n == 2){
            return n2;
        } else {
            for (int i = 2; i < n; i++){
                n3 = n1 + n2;
                n1 = n2;
                n2 = n3;
            }
            return n3;
        }
        
    }
}

不需要recursive。