Note: This is an extension of House Robber.

After robbing those houses on that street, the thief has found himself a new place for his thievery so that he will not get too much attention. This time, all houses at this place are arranged in a circle. That means the first house is the neighbor of the last one. Meanwhile, the security system for these houses remain the same as for those in the previous street.

Given a list of non-negative integers representing the amount of money of each house, determine the maximum amount of money you can rob tonight without alerting the police.

其实这个就是House Robber I的变形，II环成了一个圈，就是防止最后一个和第一个是相邻的。

class Solution {
public:
    int rob(vector<int>& nums) {
        int num = nums.size();
        if(num==0){
            return 0;
        }
        if(num==1){
            return nums[0];
        }
        
        return max(tt(nums,0,num-2),tt(nums,1,num-1));
    }
    int tt(vector<int>&nums,int l,int r){
        int a=0;
        int b=0;
        for(int i=l;i<=r;i++){
            if(i%2==0){
                a=max(a+nums[i],b);
            }else{
                b=max(a,b+nums[i]);
            }
        }
        return max(a,b);
    }
};