From 7921bf0f5d0107858abe65ae869126ab1fb7817a Mon Sep 17 00:00:00 2001
From: Keisuke KUDO <151166401+Apo-Matchbox@users.noreply.github.com>
Date: Thu, 5 Mar 2026 13:45:33 -0500
Subject: [PATCH] 142. shadowing

Add markdown file for Linked List Cycle II problem with C++ solution.
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 142/142. shadowing.md | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)
 create mode 100644 142/142. shadowing.md

diff --git a/142/142. shadowing.md b/142/142. shadowing.md
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+# (Linked List Cycle II) [https://leetcode.com/problems/linked-list-cycle-ii/description/]
+# language: C++
+
+* 今回はset
+
+```cpp
+#include <iostream>
+#include <set>
+
+struct ListNode {
+    int val;
+    ListNode* next;
+    ListNode(int x) : val(x), next(nullptr) {}
+};
+
+class Solution {
+ public:
+    ListNode *detectCycle(ListNode *head) {
+        std::set<ListNode*> reached;
+        ListNode* node = head;
+        while (node) {
+            if (reached.contains(node)) {
+                return node;
+            }
+            reached.insert(node);
+            node = node->next;
+        }
+        return nullptr;
+    }
+};
+```
+