From 210c9a145fc071f09f1c350e061cf02ac0c4ddb8 Mon Sep 17 00:00:00 2001
From: Keisuke KUDO <151166401+Apo-Matchbox@users.noreply.github.com>
Date: Fri, 1 Aug 2025 22:46:27 +0900
Subject: [PATCH] Create memo.md

---
 2/memo.md | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)
 create mode 100644 2/memo.md

diff --git a/2/memo.md b/2/memo.md
new file mode 100644
index 0000000..a81b504
--- /dev/null
+++ b/2/memo.md
@@ -0,0 +1,52 @@
+# [2. Add Two Numbers](https://leetcode.com/problems/add-two-numbers/description/)
+
+##Step1
+
+###問題意図の考察
+- Linked Listの管理ができるか
+- 数字の繰り上げ
+- 逆 -> 順　に戻して出力
+
+###解法を考える
+- これまでのLinked List カテゴリ 4題
+ * std::set
+ * std::ordered_set
+ * ListNode*
+ * dummy
+
+- 今回の問題へのアプローチ
+ * 受け取る -> 計算する -> 順に返す
+
+- 回答が思いつかなかったので、答えを見る　nktr さん (https://github.com/nktr-cp/leetcode/pull/6/commits/3c097811793a76dff4cab6d12245ea54c02857d2)
+
+```cpp
+class Solution {
+  ListNode* addTwoNumber(ListNode* l1, ListNode* l2) {
+    ListNode dummy_head = ListNode();
+    ListNode* result_tail = &dummy_head;
+    int carryover = 0;
+    while (l1 || l2 || carryover) {
+      int value = carryover;
+      if (l1) {
+        value += l1->val;
+        l1 = l1->next;
+      }
+      if (l2) {
+        value += l2->val;
+        l2 = l2->next;
+      }
+
+      carryover = value / 10;
+      value %= 10;
+
+      result_tail->next = new ListNode(value);
+      result_tail = result_tail->next;
+    }
+    return dummy_head.next;
+  }
+};
+
+```
+
+##Step2 8/1 10:50
+