This approach involves splitting the problem into two scenarios: robbing from house 0 to house n-2, and from house 1 to house n-1. The aim is to apply the linear version of the House Robber problem to each scenario separately and then take the maximum of the two resulting summed values.
Time Complexity: O(n).
Space Complexity: O(1).
1
2var robLinear = function(nums) {
3 let prev1 = 0, prev2 = 0;
4 for (const num of nums) {
5 let temp = prev1;
6 prev1 = Math.max(num + prev2, prev1);
7 prev2 = temp;
8 }
9 return prev1;
10};
11
12var rob = function(nums) {
13 if (nums.length === 1) return nums[0];
14 return Math.max(robLinear(nums.slice(0, nums.length - 1)), robLinear(nums.slice(1)));
15};
16
This JavaScript solution employs a helper function robLinear
leveraging slice function for fresh arrays without the first or last element. It calculates the maximum sum possible in both scenarios and returns the greater value.
This approach implements a memoized version of the dynamic programming solution to avoid recomputing values. We explore two scenarios of the circle, taking into account the cycles explicitly by caching intermediate results.
Time Complexity: O(n).
Space Complexity: O(n) for the memoization array.
1
2class Solution {
3 vector<int> memo;
4 int robHelper(vector<int>& nums, int start, int end) {
5 if (start >= end) return 0;
6 if (memo[start] != -1) return memo[start];
7 memo[start] = max(nums[start] + robHelper(nums, start + 2, end), robHelper(nums, start + 1, end));
8 return memo[start];
9 }
10
11public:
12 int rob(vector<int>& nums) {
13 if (nums.size() == 1) return nums[0];
14 memo.assign(nums.size(), -1);
15 int case1 = robHelper(nums, 0, nums.size() - 1);
16 memo.assign(nums.size(), -1);
17 int case2 = robHelper(nums, 1, nums.size());
18 return max(case1, case2);
19 }
20};
21
This C++ solution utilizes a memoization vector memo
for caching previously calculated outcomes of maximum rob scenario from each house index. The recursive function robHelper
operates on ranges excluding the first house once and the last house once, with the optimal result retrieved.