From e517365e8f9b129402955a66f3165cdf7b04b2de Mon Sep 17 00:00:00 2001
From: Hiro Funatsuka <hiro.funatsuka@gmail.com>
Date: Tue, 5 May 2026 14:54:03 +0900
Subject: [PATCH] Solve best time to buy and sell stock ii

---
 .../problem.md                                |  1 +
 .../step1.md                                  | 19 +++++++++++++++++++
 .../step2.md                                  | 16 ++++++++++++++++
 .../step3.md                                  | 17 +++++++++++++++++
 4 files changed, 53 insertions(+)
 create mode 100644 122_best_time_to_buy_and_sell_stock_ii/problem.md
 create mode 100644 122_best_time_to_buy_and_sell_stock_ii/step1.md
 create mode 100644 122_best_time_to_buy_and_sell_stock_ii/step2.md
 create mode 100644 122_best_time_to_buy_and_sell_stock_ii/step3.md

diff --git a/122_best_time_to_buy_and_sell_stock_ii/problem.md b/122_best_time_to_buy_and_sell_stock_ii/problem.md
new file mode 100644
index 0000000..6a7dc66
--- /dev/null
+++ b/122_best_time_to_buy_and_sell_stock_ii/problem.md
@@ -0,0 +1 @@
+## 問題: [122. Best Time to Buy and Sell Stock II](https://leetcode.com/problems/best-time-to-buy-and-sell-stock-ii/description/)
diff --git a/122_best_time_to_buy_and_sell_stock_ii/step1.md b/122_best_time_to_buy_and_sell_stock_ii/step1.md
new file mode 100644
index 0000000..048f72d
--- /dev/null
+++ b/122_best_time_to_buy_and_sell_stock_ii/step1.md
@@ -0,0 +1,19 @@
+# Step 1
+
+- 各整数を折れ線グラフの点と考え、右上がりになるものを合計に加えていく
+- 上記を実現する式: $maxProfit=maxProfit + max(prices[i] - prices[i-1], 0)$
+
+```python
+class Solution:
+    def maxProfit(self, prices: List[int]) -> int:
+        if len(prices) <= 1:
+            return 0
+        max_profit = 0
+        for i in range(1, len(prices)):
+            max_profit += max(prices[i] - prices[i - 1], 0)
+        return max_profit
+```
+
+時間計算量: $O(n)$
+
+空間計算量: $O(1)$
diff --git a/122_best_time_to_buy_and_sell_stock_ii/step2.md b/122_best_time_to_buy_and_sell_stock_ii/step2.md
new file mode 100644
index 0000000..4fae21c
--- /dev/null
+++ b/122_best_time_to_buy_and_sell_stock_ii/step2.md
@@ -0,0 +1,16 @@
+# Step 2
+
+```python
+class Solution:
+    def maxProfit(self, prices: List[int]) -> int:
+        if len(prices) < 2:
+            return 0
+        max_profit = 0
+        for i in range(1, len(prices)):
+            max_profit += max(prices[i] - prices[i - 1], 0)
+        return max_profit
+```
+
+時間計算量: $O(n)$
+
+空間計算量: $O(1)$
diff --git a/122_best_time_to_buy_and_sell_stock_ii/step3.md b/122_best_time_to_buy_and_sell_stock_ii/step3.md
new file mode 100644
index 0000000..00180d0
--- /dev/null
+++ b/122_best_time_to_buy_and_sell_stock_ii/step3.md
@@ -0,0 +1,17 @@
+# Step 3
+
+```python
+class Solution:
+    def maxProfit(self, prices: List[int]) -> int:
+        if len(prices) < 2:
+            return 0
+        max_profit = 0
+        for i in range(1, len(prices)):
+            max_profit += max(prices[i] - prices[i - 1], 0)
+        return max_profit
+```
+1回目: 0分　56秒
+
+2回目: 0分　48秒
+
+3回目: 0　53秒