剑指offer-斐波那契数列

题目

大家都知道斐波那契数列，现在要求输入一个整数n，请你输出斐波那契数列的第n项。

n<=39

链接

http://www.nowcoder.com/practice/c6c7742f5ba7442aada113136ddea0c3?tpId=13&tqId=11160&rp=1&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking

代码

class Solution {
public:
    int Fibonacci(int n) {
        if(n == 0){
            return 0;
        }
        if(n == 1 || n == 2){
            return 1;
        }
        
        int first = 1;
        int second = 1;
        int next;
        for(int index = 3; index <= n; ++ index){
            next = first + second;
            first = second;
            second = next;
        }
        
        return next;
    }
};