什么是斐波那契数列？点击这里。

解析：

1. 迭代法：

   int Fibonacci(int number){
       if(number <= 0){
           return 0;
       }
   
       if (number ==1 || number ==2){
           return 1;
       }
   
       int first = 1,second = 1,third = 0;
       for (int i =3;i <= number ;i++){
           third = first + second;
           first = second;
           second = third;
       }
       return third;
   }

    

2. 递归法：

   public int Fibonacci(int n){
       if(n <= 0){
           return 0;
       }
   
       if(n ==1 || n == 2){
           return 1;
       }
   
       return Fibonacci(n-2) + Fibonacci(n-1);
   }