From 3918dba5037f2fc298dc537f21733a4da0b674bd Mon Sep 17 00:00:00 2001
From: Hiro Funatsuka <hiro.funatsuka@gmail.com>
Date: Tue, 5 May 2026 22:02:37 +0900
Subject: [PATCH] Solve maximum subarray

---
 53_maximum_subarray/problem.md |  1 +
 53_maximum_subarray/step1.md   | 20 ++++++++++++++++++++
 53_maximum_subarray/step2.md   | 17 +++++++++++++++++
 53_maximum_subarray/step3.md   | 19 +++++++++++++++++++
 4 files changed, 57 insertions(+)
 create mode 100644 53_maximum_subarray/problem.md
 create mode 100644 53_maximum_subarray/step1.md
 create mode 100644 53_maximum_subarray/step2.md
 create mode 100644 53_maximum_subarray/step3.md

diff --git a/53_maximum_subarray/problem.md b/53_maximum_subarray/problem.md
new file mode 100644
index 0000000..450872c
--- /dev/null
+++ b/53_maximum_subarray/problem.md
@@ -0,0 +1 @@
+## 問題: [53. Maximum Subarray](https://leetcode.com/problems/maximum-subarray/description/)
diff --git a/53_maximum_subarray/step1.md b/53_maximum_subarray/step1.md
new file mode 100644
index 0000000..16d1fc3
--- /dev/null
+++ b/53_maximum_subarray/step1.md
@@ -0,0 +1,20 @@
+# Step 1
+
+- Kadaneのアルゴリズムを使う
+
+```python
+class Solution:
+    def maxSubArray(self, nums: List[int]) -> int:
+        largest_sum = -float('inf')
+        current_sum = 0
+        for num in nums:
+            current_sum = max(current_sum, 0)
+            current_sum += num
+            largest_sum = max(largest_sum, current_sum)
+        return largest_sum
+
+```
+
+時間計算量: $O(n)$
+
+空間計算量: $O(1)$
diff --git a/53_maximum_subarray/step2.md b/53_maximum_subarray/step2.md
new file mode 100644
index 0000000..c3e3da0
--- /dev/null
+++ b/53_maximum_subarray/step2.md
@@ -0,0 +1,17 @@
+# Step 2
+
+```python
+class Solution:
+    def maxSubArray(self, nums: List[int]) -> int:
+        largest_sum = -float('inf')
+        current_sum = 0
+        for num in nums:
+            current_sum = max(current_sum, 0) + num
+            largest_sum = max(largest_sum, current_sum)
+        return largest_sum
+
+```
+
+時間計算量: $O(n)$
+
+空間計算量: $O(1)$
diff --git a/53_maximum_subarray/step3.md b/53_maximum_subarray/step3.md
new file mode 100644
index 0000000..8a8a723
--- /dev/null
+++ b/53_maximum_subarray/step3.md
@@ -0,0 +1,19 @@
+# Step 3
+
+```python
+class Solution:
+    def maxSubArray(self, nums: List[int]) -> int:
+        largest_sum = -float('inf')
+        current_sum = 0
+        for num in nums:
+            current_sum = max(current_sum, 0) + num
+            largest_sum = max(largest_sum, current_sum)
+        return largest_sum
+
+```
+
+1回目: 1分　26秒
+
+2回目: 1分　8秒
+
+3回目: 1分　5秒