From ddc8e2de604813772abe857bd7e7906ef2837fa0 Mon Sep 17 00:00:00 2001
From: mengyi <yiii9292@gmail.com>
Date: Sun, 9 Jun 2024 21:30:32 -0400
Subject: [PATCH] update project 203 java version solution

---
 problems/0203.移除链表元素.md | 54 ++++++++++++++++-------------
 1 file changed, 30 insertions(+), 24 deletions(-)

diff --git a/problems/0203.移除链表元素.md b/problems/0203.移除链表元素.md
index efcc6414..64124fbb 100644
--- a/problems/0203.移除链表元素.md
+++ b/problems/0203.移除链表元素.md
@@ -224,9 +224,10 @@ struct ListNode* removeElements(struct ListNode* head, int val){
 
 ### Java：
 
+用原来的链表操作：
 ```java
 /**
- * 添加虚节点方式
+ * 方法1
  * 时间复杂度 O(n)
  * 空间复杂度 O(1)
  * @param head
@@ -234,25 +235,22 @@ struct ListNode* removeElements(struct ListNode* head, int val){
  * @return
  */
 public ListNode removeElements(ListNode head, int val) {
-    if (head == null) {
-        return head;
+    while(head!=null && head.val==val) {
+        head = head.next;
     }
-    // 因为删除可能涉及到头节点，所以设置dummy节点，统一操作
-    ListNode dummy = new ListNode(-1, head);
-    ListNode pre = dummy;
-    ListNode cur = head;
-    while (cur != null) {
-        if (cur.val == val) {
-            pre.next = cur.next;
+    ListNode curr = head;
+    while(curr!=null && curr.next !=null) {
+        if(curr.next.val == val){
+            curr.next = curr.next.next;
         } else {
-            pre = cur;
+            curr = curr.next;
         }
-        cur = cur.next;
     }
-    return dummy.next;
+    return head;
 }
+
 /**
- * 不添加虚拟节点方式
+ * 方法1
  * 时间复杂度 O(n)
  * 空间复杂度 O(1)
  * @param head
@@ -280,8 +278,13 @@ public ListNode removeElements(ListNode head, int val) {
     }
     return head;
 }
+
+```
+
+设置一个虚拟头结点：
+
+```java
 /**
- * 不添加虚拟节点and pre Node方式
  * 时间复杂度 O(n)
  * 空间复杂度 O(1)
  * @param head
@@ -289,18 +292,21 @@ public ListNode removeElements(ListNode head, int val) {
  * @return
  */
 public ListNode removeElements(ListNode head, int val) {
-    while(head!=null && head.val==val){
-        head = head.next;
-    }
-    ListNode curr = head;
-    while(curr!=null){
-        while(curr.next!=null && curr.next.val == val){
-            curr.next = curr.next.next;
+    // 设置一个虚拟的头结点
+    ListNode dummy = new ListNode();
+    dummy.next = head;
+
+    ListNode cur = dummy;
+    while (cur.next != null) {
+        if (cur.next.val == val) {
+            cur.next = cur.next.next;
+        } else {
+            cur = cur.next;        
         }
-        curr = curr.next;
     }
-    return head;
+    return dummy.next;
 }
+
 ```
 
 ### Python：