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 };