23--house-robber-ii.java

class Solution {
    public int rob(int[] nums) {
        int n = nums.length;
        if (n == 1) return nums[0];
        if (n == 2) return Math.max(nums[0], nums[1]);
        return Math.max(rob(nums, 0, n - 2), rob(nums, 1, n - 1));
    }
    public int rob(int[] nums, int start, int end) {
        int prev1 = nums[start];
        int prev2 = Math.max(nums[start], nums[start + 1]);
        for (int i = start + 2; i <= end; i++) {
            int curr = Math.max(nums[i] + prev1, prev2);
            prev1 = prev2;
            prev2 = curr;
        }
        return prev2;
    }
} // TC: O(n), SC: O(1),, max-cosecutives ones