LintCode：Fibonacci

C++

 class Solution{
 public:
     /**
      * @param n: an integer
      * @return an integer f(n)
      */
     int fibonacci(int n) {
         // write your code here
         int a=,b=;
         for (int i=; i<n; i++) {
             a = a+b;
             b = a-b;
         }
         return a;
     }
 };