牛客网-《剑指offer》-斐波那契数列

题目：http://www.nowcoder.com/practice/c6c7742f5ba7442aada113136ddea0c3

C++

 1 class Solution {
 2 public:
 3     int Fibonacci(int n) {
 4         if (n == 0) return 0;
 5         if (n <= 2) return 1;
 6         
 7         int a = 1, b = 1;
 8         while(n-- > 2) {
 9             a = a + b;
10             b = a - b;
11         }
12         return a;
13 
14     }
15 };