LintCode斐波纳契数列题目：分析小结

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

class Solution {
    /**
     * @param n: an integer
     * @return an integer f(n)
     */
    public int fibonacci(int n) {
        // write your code here
        if(n == 1)
        {
            return 0;
        }
        else if(n == 2)
        {
            return 1;
        }
        else
        {
            int s1 = 0;
            int s2 = 1;
            int sum = 0;
            int i = 3;
            while(i <= n)
            {
                sum = s1 + s2;
                s1 = s2;
                s2 =sum;
                i++;
            }
            return sum;
        }
    }
}