diff --git a/198/memo.md b/198/memo.md
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+# 198. House Robber
+
+- 動的計画法を書いた
+
+
+https://github.com/naoto-iwase/leetcode/pull/40
+の実装2: without_lastとwith_lastの二変数だけで良い
+- sol2.py
+
+> このコードはスレッドセーフティーという意味でどうなっているでしょうか。
+
+- cacheを使う場合（メモ化再帰）、キャッシュはthread safe: multi-threadで使用できる
+
+https://github.com/hroc135/leetcode/pull/33#discussion_r1899009212
+> フィボナッチになりそうですね。黄金比の n 乗なので 1.6^n くらいです
+メモがない場合の計算量
+https://ja.wikipedia.org/wiki/%E3%83%95%E3%82%A3%E3%83%9C%E3%83%8A%E3%83%83%E3%83%81%E6%95%B0
+
+
+メモ化再帰も書いておく (sol3.py)
diff --git a/198/sol1.py b/198/sol1.py
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+class Solution:
+    def rob(self, nums: List[int]) -> int:
+        if not nums:
+            raise ValueError("The input list is empty")
+
+        if len(nums) < 2:
+            return max(nums)
+
+        max_nums = [nums[0], max(nums[0], nums[1])] + [0] * (len(nums) - 2)
+
+        for i in range(2, len(nums)):
+            max_nums[i] = max(max_nums[i - 1], max_nums[i - 2] + nums[i])
+
+        return max_nums[-1]
diff --git a/198/sol2.py b/198/sol2.py
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+class Solution:
+    def rob(self, nums: List[int]) -> int:
+        if not nums:
+            raise ValueError("The input list is empty")
+
+        if len(nums) < 2:
+            return max(nums)
+
+        max_with_last = nums[0]
+        max_without_last = 0
+
+        for i in range(1, len(nums)):
+            next_max_without_last = max_with_last
+            max_with_last = max(max_with_last, max_without_last + nums[i])
+            max_without_last = next_max_without_last
+
+        return max_with_last
diff --git a/198/sol3.py b/198/sol3.py
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+from functools import cache
+
+
+class Solution:
+    def rob(self, nums: List[int]) -> int:
+        if not nums:
+            raise ValueError("The input list is empty")
+
+        @cache
+        def rob_helper(idx):
+            if idx < 2:
+                return max(nums[: idx + 1])
+
+            return max(rob_helper(idx - 1), rob_helper(idx - 2) + nums[idx])
+
+        return rob_helper(len(nums) - 1)