HouseRobberII.cpp

//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.a

#include<vector>
#include<algorithm>

using namespace std;

class HouseRobberII {
public:
	int rob(vector<int>& nums) {
		int n = nums.size();
		if (n < 2) return n ? nums[0] : 0;
		return max(robber(nums, 0, n - 2), robber(nums, 1, n - 1));
	}
private:
	int robber(vector<int>& nums, int l, int r) {
		int pre = 0, cur = 0;
		for (int i = l; i <= r; i++) {
			int temp = max(pre + nums[i], cur);
			pre = cur;
			cur = temp;
		}
		return cur;
	}
};