solved 'House Robber II' on leetcode https://leetcode.com/problems/house-robber-ii/

rob_ii.cc

class Solution {
public:
    int rob(vector<int>& nums) {
        int nums_len = nums.size();
        if (nums_len == 0) {
            return 0;
        }
        else if (nums_len == 1) {
            return nums[0];
        }

        // Fix choosing the first place.
        int max_prev_prev = nums[0],
            max_prev = nums[0];
        // The last place cannot be chosen!
        for (int i = 2; i < nums_len - 1; ++i) {
            int max_curr = max(max_prev_prev + nums[i], max_prev);
            max_prev_prev = max_prev;
            max_prev = max_curr;
        }
        int max_to_rub_fix_first = max(max_prev_prev, max_prev);

        // Another round, fix the second space.
        max_prev_prev = 0;
        max_prev = nums[1];
        // It's fine to choose the last place in this case.
        for (int i = 2; i < nums_len; ++i) {
            int max_curr = max(max_prev_prev + nums[i], max_prev);
            max_prev_prev = max_prev;
            max_prev = max_curr;
        }
        int max_to_rub_fix_second = max(max_prev_prev, max_prev);

        return max(max_to_rub_fix_first, max_to_rub_fix_second);
    }
};