From 5218596c0aaa622f7678ba88723a1c7d7d3516fd Mon Sep 17 00:00:00 2001
From: zhangsan <646228430@qq.com>
Date: Fri, 14 Mar 2025 20:12:38 +0800
Subject: [PATCH] =?UTF-8?q?3.14=20=E9=93=BE=E8=A1=A8?=
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---
 .../java/linkedlist/GetIntersectionNode.java  | 40 +++++++++++++
 src/main/java/linkedlist/IsPalindrome.java    | 58 +++++++++++++++++++
 src/main/java/linkedlist/ListNode.java        | 10 ++++
 src/main/java/linkedlist/ReverseList.java     | 21 +++++++
 4 files changed, 129 insertions(+)
 create mode 100644 src/main/java/linkedlist/GetIntersectionNode.java
 create mode 100644 src/main/java/linkedlist/IsPalindrome.java
 create mode 100644 src/main/java/linkedlist/ListNode.java
 create mode 100644 src/main/java/linkedlist/ReverseList.java

diff --git a/src/main/java/linkedlist/GetIntersectionNode.java b/src/main/java/linkedlist/GetIntersectionNode.java
new file mode 100644
index 0000000..271d489
--- /dev/null
+++ b/src/main/java/linkedlist/GetIntersectionNode.java
@@ -0,0 +1,40 @@
+package linkedlist;
+
+import java.util.HashSet;
+
+/**
+ * 题目：160. 相交链表  (getIntersectionNode)
+ * 描述：给你两个单链表的头节点 headA 和 headB ，请你找出并返回两个单链表相交的起始节点。如果两个链表不存在相交节点，返回 null 。
+
+ * 链接：https://leetcode.cn/problems/intersection-of-two-linked-lists/
+
+ */
+
+//没想出高效方法
+public class GetIntersectionNode {
+    public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
+        HashSet<ListNode> visited = new HashSet<ListNode>();
+        ListNode temp = headA;
+        while (temp != null) {
+            visited.add(temp);
+            temp = temp.next;
+        }
+        temp = headB;
+        while (temp != null) {
+            if (visited.contains(temp)) {
+                return temp;
+            }
+            temp = temp.next;
+        }
+        return null;
+    }
+    //高效方法
+    public ListNode getIntersectionNode1(ListNode headA, ListNode headB) {
+        ListNode A = headA, B = headB;
+        while (A != B) {
+            A = A != null ? A.next : headB;
+            B = B != null ? B.next : headA;
+        }
+        return A;
+    }
+}
diff --git a/src/main/java/linkedlist/IsPalindrome.java b/src/main/java/linkedlist/IsPalindrome.java
new file mode 100644
index 0000000..219e3a1
--- /dev/null
+++ b/src/main/java/linkedlist/IsPalindrome.java
@@ -0,0 +1,58 @@
+package linkedlist;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * 题目：234. 回文链表  (isPalindrome)
+ * 描述：给你一个单链表的头节点 head ，请你判断该链表是否为回文链表。如果是，返回 true ；否则，返回 false 。
+
+ * 链接：https://leetcode.cn/problems/palindrome-linked-list/
+
+ */
+public class IsPalindrome {
+    public boolean isPalindrome(ListNode head) {
+        ListNode temp=head;
+        List<Integer>list=new ArrayList<>();
+        while (head!=null){
+            list.add(head.val);
+            head=head.next;
+        }
+        int size=list.size();
+        for (int i = 0; i < size; i++) {
+            if(list.get(i)!=list.get(size-1-i))
+                return false;
+        }
+        return true;
+    }
+    //快慢指针 + 链表反转
+    public boolean isPalindrome1(ListNode head) {
+        if (head == null || head.next == null) {
+            return true; // 空链表或只有一个节点，直接返回 true
+        }
+
+        // 1. 快慢指针找到链表中点
+        ListNode slow = head;
+        ListNode fast = head;
+        while (fast != null && fast.next != null) {
+            slow = slow.next;
+            fast = fast.next.next;
+        }
+        ReverseList reverseList = new ReverseList();
+        // 2. 反转后半部分链表
+        ListNode secondHalf = reverseList.reverseList(slow);
+
+        // 3. 比较前后两部分链表
+        ListNode p1 = head;
+        ListNode p2 = secondHalf;
+        while (p2 != null) {
+            if (p1.val != p2.val) {
+                return false;
+            }
+            p1 = p1.next;
+            p2 = p2.next;
+        }
+
+        return true;
+    }
+}
diff --git a/src/main/java/linkedlist/ListNode.java b/src/main/java/linkedlist/ListNode.java
new file mode 100644
index 0000000..dd18f39
--- /dev/null
+++ b/src/main/java/linkedlist/ListNode.java
@@ -0,0 +1,10 @@
+package linkedlist;
+
+public class ListNode {
+    int val;
+    ListNode next;
+    ListNode(int x) {
+        val = x;
+        next = null;
+    }
+}
diff --git a/src/main/java/linkedlist/ReverseList.java b/src/main/java/linkedlist/ReverseList.java
new file mode 100644
index 0000000..9549180
--- /dev/null
+++ b/src/main/java/linkedlist/ReverseList.java
@@ -0,0 +1,21 @@
+package linkedlist;
+/**
+ * 题目：206. 反转链表  (reverseList)
+ * 描述：给你单链表的头节点 head ，请你反转链表，并返回反转后的链表。
+
+ * 链接：https://leetcode.cn/problems/reverse-linked-list/
+
+ */
+public class ReverseList {
+    public ListNode reverseList(ListNode head) {
+        ListNode prev = null;
+        ListNode curr = head;
+        while (curr != null) {
+            ListNode next = curr.next;
+            curr.next = prev;
+            prev = curr;
+            curr = next;
+        }
+        return prev;
+    }
+}