From 929cbe2931b645d031f9e99cc20be74260e9e873 Mon Sep 17 00:00:00 2001
From: tom4649 <tkaaynakiyoshi@gmail.com>
Date: Sat, 28 Mar 2026 16:30:33 +0900
Subject: [PATCH 1/2] 198. House Robber

---
 198/memo.md | 20 ++++++++++++++++++++
 198/sol1.py | 11 +++++++++++
 198/sol2.py | 14 ++++++++++++++
 198/sol3.py | 13 +++++++++++++
 4 files changed, 58 insertions(+)
 create mode 100644 198/memo.md
 create mode 100644 198/sol1.py
 create mode 100644 198/sol2.py
 create mode 100644 198/sol3.py

diff --git a/198/memo.md b/198/memo.md
new file mode 100644
index 0000000..660c1b9
--- /dev/null
+++ b/198/memo.md
@@ -0,0 +1,20 @@
+# 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
new file mode 100644
index 0000000..42fa801
--- /dev/null
+++ b/198/sol1.py
@@ -0,0 +1,11 @@
+class Solution:
+    def rob(self, nums: List[int]) -> int:
+        if len(nums) < 2:
+            return max(nums)
+
+        max_nums = [nums[0], max(nums[0], nums[1])]
+
+        for i in range(2, len(nums)):
+            max_nums.append(max(max_nums[i - 2], max_nums[i - 1] + nums[i]))
+
+        return max_nums[-1]
diff --git a/198/sol2.py b/198/sol2.py
new file mode 100644
index 0000000..84dbec8
--- /dev/null
+++ b/198/sol2.py
@@ -0,0 +1,14 @@
+class Solution:
+    def rob(self, nums: List[int]) -> int:
+        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
new file mode 100644
index 0000000..01cff22
--- /dev/null
+++ b/198/sol3.py
@@ -0,0 +1,13 @@
+from functools import cache
+
+
+class Solution:
+    def rob(self, nums: List[int]) -> int:
+        @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)

From 8e6f5c71b3c8917e6c745b90efc60053a44dd1e9 Mon Sep 17 00:00:00 2001
From: tom4649 <tkaaynakiyoshi@gmail.com>
Date: Sun, 29 Mar 2026 17:29:51 +0900
Subject: [PATCH 2/2] Add suggested changes

---
 198/sol1.py | 7 +++++--
 198/sol2.py | 3 +++
 198/sol3.py | 3 +++
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/198/sol1.py b/198/sol1.py
index 42fa801..0f6f474 100644
--- a/198/sol1.py
+++ b/198/sol1.py
@@ -1,11 +1,14 @@
 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])]
+        max_nums = [nums[0], max(nums[0], nums[1])] + [0] * (len(nums) - 2)
 
         for i in range(2, len(nums)):
-            max_nums.append(max(max_nums[i - 2], max_nums[i - 1] + nums[i]))
+            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
index 84dbec8..02fb250 100644
--- a/198/sol2.py
+++ b/198/sol2.py
@@ -1,5 +1,8 @@
 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)
 
diff --git a/198/sol3.py b/198/sol3.py
index 01cff22..b755922 100644
--- a/198/sol3.py
+++ b/198/sol3.py
@@ -3,6 +3,9 @@
 
 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: