From c901cc9d0fce210f930a7498099481aabbbfbb2a Mon Sep 17 00:00:00 2001
From: aiueoriku <112373068+aiueoriku@users.noreply.github.com>
Date: Tue, 20 May 2025 12:11:51 +0900
Subject: [PATCH 1/4] Create TwySum.md

---
 TwoSum/TwySum.md | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
 create mode 100644 TwoSum/TwySum.md

diff --git a/TwoSum/TwySum.md b/TwoSum/TwySum.md
new file mode 100644
index 0000000..b42fe14
--- /dev/null
+++ b/TwoSum/TwySum.md
@@ -0,0 +1,17 @@
+"""python
+class Solution(object):
+    def twoSum(self, nums, target):
+        """
+        :type nums: List[int]
+        :type target: int
+        :rtype: List[int]
+        """
+        for i in range(len(nums)):
+            for j in range(i+1, len(nums)):
+                if nums[i]+nums[j]==target:
+                    return [i,j]
+                    break
+"""
+
+# 感想
+forループを2つ回して愚直に行ったが，より効率の良いアルゴリズムがありそう．

From 28e9a53237501707fefd7e15b30c6543b34d6051 Mon Sep 17 00:00:00 2001
From: aiueoriku <112373068+aiueoriku@users.noreply.github.com>
Date: Tue, 20 May 2025 12:38:59 +0900
Subject: [PATCH 2/4] Update and rename TwySum.md to TwoSum.md

---
 TwoSum/{TwySum.md => TwoSum.md} | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
 rename TwoSum/{TwySum.md => TwoSum.md} (96%)

diff --git a/TwoSum/TwySum.md b/TwoSum/TwoSum.md
similarity index 96%
rename from TwoSum/TwySum.md
rename to TwoSum/TwoSum.md
index b42fe14..6d55ff2 100644
--- a/TwoSum/TwySum.md
+++ b/TwoSum/TwoSum.md
@@ -1,4 +1,5 @@
-"""python
+```python
+
 class Solution(object):
     def twoSum(self, nums, target):
         """
@@ -11,7 +12,7 @@ class Solution(object):
                 if nums[i]+nums[j]==target:
                     return [i,j]
                     break
-"""
+```
 
 # 感想
 forループを2つ回して愚直に行ったが，より効率の良いアルゴリズムがありそう．

From 29422c97ab80ee4cdf2ab8354d09c22db17641f0 Mon Sep 17 00:00:00 2001
From: aiueoriku <112373068+aiueoriku@users.noreply.github.com>
Date: Tue, 20 May 2025 15:21:32 +0900
Subject: [PATCH 3/4] do step1,2, and 3

---
 TwoSum/TwoSum.md | 53 ++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 51 insertions(+), 2 deletions(-)

diff --git a/TwoSum/TwoSum.md b/TwoSum/TwoSum.md
index 6d55ff2..1199133 100644
--- a/TwoSum/TwoSum.md
+++ b/TwoSum/TwoSum.md
@@ -1,3 +1,6 @@
+# Step 1
+まずは愚直に実行
+
 ```python
 
 class Solution(object):
@@ -13,6 +16,52 @@ class Solution(object):
                     return [i,j]
                     break
 ```
+実行時間は2271ms
+
+
+
+# Step 2
+PRや公式解答を参照．
+解答を見るとhashmapという手法を発見．dictを用いることで高速に探索出来るらしい．
+keyの操作に慣れていないので，デバッグしつつ実装
+```python
+class Solution(object):
+    def twoSum(self, nums, target):
+        """
+        :type nums: List[int]
+        :type target: int
+        :rtype: List[int]
+        """
+        hashmap = {}
+        for i in range(len(nums)):
+            hashmap[nums[i]] = i
+        print(nums) # [2, 7, 11, 15]
+        print(hashmap) # {15: 3, 2: 0, 11: 2, 7: 1}
+        for i in range(len(nums)):
+            complement = target - nums[i]
+            if complement in hashmap and hashmap[complement] != i: # dict[key]=value
+                return [i, hashmap[complement]]
+        return []
+```
+実行時間は158ms．計算量を減らすことが出来た．
 
-# 感想
-forループを2つ回して愚直に行ったが，より効率の良いアルゴリズムがありそう．
+# Step 3
+何も見ないで実装
+```python
+class Solution(object):
+    def twoSum(self, nums, target):
+        """
+        :type nums: List[int]
+        :type target: int
+        :rtype: List[int]
+        """
+        hashmap = {}
+        for i in range(len(nums)):
+            hashmap[nums[i]] = i
+        for i in range(len(nums)):
+            complement = target - nums[i]
+            if complement in hashmap and hashmap[complement]!=i:
+                return [i, hashmap[complement]]
+        return []
+```
+実行時間は5ms同じコードなのに実行時間が違う．他に見るべき指標があるかも．

From c5367f19562f518b40585fbdd1d5f8920b1964e1 Mon Sep 17 00:00:00 2001
From: aiueoriku <112373068+aiueoriku@users.noreply.github.com>
Date: Wed, 21 May 2025 09:22:27 +0900
Subject: [PATCH 4/4] add Step4
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

いただいたアドバイスを元にStep4を追記
---
 TwoSum/TwoSum.md | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/TwoSum/TwoSum.md b/TwoSum/TwoSum.md
index 1199133..4cc1bc8 100644
--- a/TwoSum/TwoSum.md
+++ b/TwoSum/TwoSum.md
@@ -65,3 +65,32 @@ class Solution(object):
         return []
 ```
 実行時間は5ms同じコードなのに実行時間が違う．他に見るべき指標があるかも．
+
+# Step 4
+いただいたアドバイスを元に実装
+```python
+class Solution:
+    def twoSum(self, nums: List[int], target: int) -> List[int]:
+        num_to_index = {}
+        for i in range (len(nums)):
+            complement = target - nums[i]
+            if complement in num_to_index and num_to_index[complement]!=i:
+                return [i, num_to_index[complement]]
+            num_to_index[nums[i]] = i
+        return []
+```
+辞書の名前をnum_to_indexに変更して意味を分かりやすくした．
+for文を1つにまとめた．
+
+```python
+class Solution:
+    def twoSum(self, nums: List[int], target: int) -> List[int]:
+        num_to_index = {}
+        for i, num in enumerate(nums):
+            complement = target - num
+            if complement in num_to_index and num_to_index[complement]!=i:
+                return [num_to_index[complement], i]
+            num_to_index[num] = i
+        return []
+```
+enumerateでも書いてみた．個人的にはこちらのほうが好みかも．