Update 0198-house-robber.kt

Author: a93a

kotlin/0198-house-robber.kt

@@ -1,5 +1,6 @@
+// DP Time O(n) and Space O(1)
 class Solution {
-	fun rob(nums: IntArray): Int {
+    fun rob(nums: IntArray): Int {
         var rob = 0
         var notRob = 0
         nums.forEach {
@@ -10,4 +11,44 @@ class Solution {
 
         return maxOf(rob, notRob)
     }
-}
+}
+
+// DP Time O(n) and Space O(n)
+class Solution {
+    fun rob(nums: IntArray): Int {
+        val n = nums.size
+        val dp = IntArray (n)
+        dp[0] = nums[0]
+
+        for (i in 1 until n) {
+            dp[i] = maxOf(
+                nums[i] + if (i > 1) dp[i - 2] else 0,
+                dp[i - 1]
+            )
+        }
+
+        return dp[n - 1]
+    }
+}
+
+// Recursion + memoization Time O(n) and Space O(n)
+class Solution {
+    fun rob(nums: IntArray): Int {
+        val n = nums.size
+        val dp = IntArray (n) { -1 }
+
+        fun dfs(i: Int): Int {
+            if (i >= n) return 0
+            if (dp[i] != -1) return dp[i]
+
+            dp[i] = maxOf(
+                nums[i] + dfs(i + 2),
+                dfs(i + 1)
+            )
+
+            return dp[i]
+        }
+
+        return dfs(0)
+    }
+}