LeetCode - House Robber II

Question Definition

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.

Java Solution

class Solution {
    public int rob(int[] nums) {
        if (nums.length <= 1) return nums.length == 0 ? 0 : nums[0];
        return Math.max(rob(nums, 0, nums.length - 1), rob(nums, 1, nums.length));
    }

    private int rob(int[] nums, int left, int right) {
        if (right - left <= 1) return nums[left];
        int[] dp = new int[right];
        dp[left] = nums[left];
        dp[left + 1] = Math.max(nums[left], nums[left + 1]);
        for (int i = left + 2; i < right; ++i) {
            dp[i] = Math.max(nums[i] + dp[i - 2], dp[i - 1]);
        }
        return dp[right - 1];
    }
}