剑指offer——斐波那契数列

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

class Solution {
public:
    int Fibonacci(int n) {
        int first = 0, second = 1,target=0;
        if (n < 2)
            return n ;
        for (int i = 0; i < n-1; i++)
        {
            target = first + second;
            first = second;
            second = target;
        }
        return target;
    }
};