206:反转链表

src/main/java/leetcode/editor/cn/ReverseLinkedList.java

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+//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。
+// 
+// 
+// 
+//
+// 示例 1： 
+//
+// 
+//输入：head = [1,2,3,4,5]
+//输出：[5,4,3,2,1]
+// 
+//
+// 示例 2： 
+//
+// 
+//输入：head = [1,2]
+//输出：[2,1]
+// 
+//
+// 示例 3： 
+//
+// 
+//输入：head = []
+//输出：[]
+// 
+//
+// 
+//
+// 提示： 
+//
+// 
+// 链表中节点的数目范围是 [0, 5000] 
+// -5000 <= Node.val <= 5000 
+// 
+//
+// 
+//
+// 进阶：链表可以选用迭代或递归方式完成反转。你能否用两种方法解决这道题？ 
+// 
+// 
+// Related Topics 链表 
+// 👍 1777 👎 0
+
+package leetcode.editor.cn;
+
+import com.code.leet.entiy.ListNode;
+
+//206:反转链表
+public class ReverseLinkedList{
+    public static void main(String[] args) {
+        //测试代码
+        Solution solution = new ReverseLinkedList().new Solution();
+    }
+    //力扣代码
+    //leetcode submit region begin(Prohibit modification and deletion)
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+class Solution {
+    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;
+    }
+}
+//leetcode submit region end(Prohibit modification and deletion)
+
+}

src/main/java/leetcode/editor/cn/ReverseLinkedList.md

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+给你单链表的头节点 <code>head</code> ，请你反转链表，并返回反转后的链表。
+<div class="original__bRMd">
+<div>
+<p> </p>
+
+<p><strong>示例 1：</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2021/02/19/rev1ex1.jpg" style="width: 542px; height: 222px;" />
+<pre>
+<strong>输入：</strong>head = [1,2,3,4,5]
+<strong>输出：</strong>[5,4,3,2,1]
+</pre>
+
+<p><strong>示例 2：</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2021/02/19/rev1ex2.jpg" style="width: 182px; height: 222px;" />
+<pre>
+<strong>输入：</strong>head = [1,2]
+<strong>输出：</strong>[2,1]
+</pre>
+
+<p><strong>示例 3：</strong></p>
+
+<pre>
+<strong>输入：</strong>head = []
+<strong>输出：</strong>[]
+</pre>
+
+<p> </p>
+
+<p><strong>提示：</strong></p>
+
+<ul>
+	<li>链表中节点的数目范围是 <code>[0, 5000]</code></li>
+	<li><code>-5000 <= Node.val <= 5000</code></li>
+</ul>
+
+<p> </p>
+
+<p><strong>进阶：</strong>链表可以选用迭代或递归方式完成反转。你能否用两种方法解决这道题？</p>
+</div>
+</div>
+<div><div>Related Topics</div><div><li>链表</li></div></div>\n<div><li>👍 1777</li><li>👎 0</li></div>