leetcode 206 reverse List

src/main/java/io/github/ehlxr/leetcode/ListNode.java

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+/*
+ * The MIT License (MIT)
+ *
+ * Copyright © 2020 xrv <xrg@live.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package io.github.ehlxr.leetcode;
+
+/**
+ * 链表结构
+ *
+ * @author ehlxr
+ * @since 2021-02-27 21:09.
+ */
+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;
+    }
+
+    @Override
+    public String toString() {
+        return "ListNode{" +
+                "val=" + val +
+                ", next=" + next +
+                '}';
+    }
+}

src/main/java/io/github/ehlxr/leetcode/Solution206.java

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+/*
+ * The MIT License (MIT)
+ *
+ * Copyright © 2020 xrv <xrg@live.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package io.github.ehlxr.leetcode;
+
+/**
+ * 反转链表
+ * 假设链表为 1 → 2 → 3 → null，我们想要把它改成 null ← 1 ← 2 ← 3
+ *
+ * @author ehlxr
+ * @since 2021-02-27 21:08.
+ */
+public class Solution206 {
+    /*
+    方法一：迭代
+    https://leetcode-cn.com/problems/reverse-linked-list/solution/fan-zhuan-lian-biao-by-leetcode-solution-d1k2/
+    */
+    public static ListNode reverseList1(ListNode head) {
+        ListNode prev = null;
+        while (head != null) {
+            // 先存储当前节点的下一个节点
+            ListNode next = head.next;
+
+            // 将当前节点的下一个节点改为前一个节点
+            head.next = prev;
+
+            // 指针后移
+            // 更改前一个节点为当前节点
+            prev = head;
+            // 更改当前节点为下一个节点
+            head = next;
+        }
+
+        return prev;
+    }
+
+    /*
+    方法一：递归
+    https://leetcode-cn.com/problems/reverse-linked-list/solution/shi-pin-jiang-jie-die-dai-he-di-gui-hen-hswxy/
+    */
+    public static ListNode reverseList2(ListNode head) {
+        // 递归终止条件
+        if (head == null || head.next == null) {
+            return head;
+        }
+
+        ListNode h = reverseList2(head.next);
+
+        head.next.next = head;
+        // 防止链表循环
+        head.next = null;
+
+        return h;
+    }
+
+    public static void main(String[] args) {
+        ListNode n1 = new ListNode(1);
+        ListNode n2 = new ListNode(2);
+        ListNode n3 = new ListNode(3);
+        ListNode n4 = new ListNode(4);
+
+        n1.next = n2;
+        n2.next = n3;
+        n3.next = n4;
+
+        System.out.println(n1);
+
+        System.out.println(reverseList2(n1));
+    }
+}

src/main/java/io/github/ehlxr/lock/Locker.java

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+/*
+ * The MIT License (MIT)
+ *
+ * Copyright © 2020 xrv <xrg@live.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package io.github.ehlxr.lock;
+
+import java.util.concurrent.locks.AbstractQueuedLongSynchronizer;
+import java.util.concurrent.locks.ReentrantLock;
+
+/**
+ * @author ehlxr
+ * @since 2021-02-15 18:11.
+ */
+public class Locker {
+
+
+    public static void main(String[] args) {
+        ReentrantLock lock = new ReentrantLock();
+
+        lock.tryLock();
+    }
+
+}