题解 | #上台阶#C++暴力动态规划解法，非递归

class GoUpstairs {
public:
    int countWays(int n) 
    {
        if(n==1)
        {
            return 0;
        }
        if(n==2)
        {
            return 1;
        }
        if(n==3)
        {
            return 2;
        }
        else 
        {
            vector <int> d;
            int i=0;
            d.push_back(0);
            d.push_back(1);
            d.push_back(2);
            for(i=3;i<n;i++)
            {
                d.push_back(d[i-1]%1000000007+d[i-2]%1000000007);
            }
            return d[n-1]%1000000007;
        }
        return 0;   
    }
};