HouseRobberII.java

public class HouseRobberII {
 public int rob(int[] nums) {
 if(nums.length == 1) return nums[0];
 return Math.max(robHelper(nums, 0, nums.length - 1), robHelper(nums, 1, nums.length));
 }

 private int robHelper(int[] nums, int start, int end) {
 int include = 0;
 int exclude = 0;
 for(int i = start; i < end; i++) {
 int lastInclude = include;
 include = exclude + nums[i];
 exclude = Math.max(lastInclude, exclude);
 }
 return Math.max(include, exclude);
 }
}