solve: houseRobberIi

Author: yolophg

house-robber-ii/yolophg.py

@@ -0,0 +1,32 @@
+# Time Complexity: O(n) -> iterate through the houses twice, each in O(n) time.
+# Space Complexity: O(1) -> use a few extra variables, no additional data structures.
+
+class Solution:
+    def rob(self, nums: List[int]) -> int:        
+        if not nums:
+            return 0
+        if len(nums) == 1:
+            return nums[0]
+        
+        # track the max money from two houses before and last house.
+        var1, var2 = 0, 0  
+        
+        # robbing from first house to second-last house (excluding last house)
+        for i in nums[:-1]:
+            # store previous max before updating.
+            temp = var1  
+            # either rob this house or skip it.
+            var1 = max(var2 + i, var1)  
+            # move to the next house.
+            var2 = temp  
+        
+        # same logic, but robbing from second house to last house.
+        vaar1, vaar2 = 0, 0  
+        
+        for i in nums[1:]:
+            temp = vaar1
+            vaar1 = max(vaar2 + i, vaar1)
+            vaar2 = temp
+        
+        # take the max of both cases.
+        return max(var1, vaar1)