剑指 Offer 14- I. 剪绳子

class Solution {
public:
    int cuttingRope(int n) {
        if (n<4) return n-1;// n=2，返回1, n=3, 返回2

        int k = n / 3;
        int res;
        if(n%3==1){
            res = pow(3, k-1) * 2 * 2;
        }else if (n%3==2){
            res = pow(3, k) * 2;
        }else{
            res = pow(3,k);
        }

        return res;
    }
};