Fibonacci Number

Fib数, 当前数等于前两个数的和, 需要记录一下前两个数即可.

class Solution {
    public int fib(int n) {
        if(n == 0)
            return 0;
        if(n == 1)
            return 1;
        int first = 0;
        int second = 1;
        int current = 1;
        for(int i = 2; i <= n; i++) {
            current = first + second;
            first = second;
            second = current;
        }
        return current;
    }
}