斐波那契数列非递归算法

class Solution {  
public:  
    int Fibonacci(int n) {  
        int res[2] = {0,1};  
        if(n<=1)  
            return res[n];  
          
        int num1 = 1;  
        int num2 = 0;  
        int sum = 0;  
          
        for(int i = 2;i<=n;i++)  
        {  
            sum = num1+num2;  
            num2 = num1;  
            num1 = sum;  
        }  
          
        return sum;  
    }  
};