java實現(xiàn)鏈表反轉(zhuǎn)

更新時間：2021年08月17日 11:36:40 作者：奮斗的二哈

這篇文章主要為大家詳細介紹了java實現(xiàn)鏈表反轉(zhuǎn)，分別通過迭代法、遞歸法實現(xiàn)java鏈表反轉(zhuǎn)，文中示例代碼介紹的非常詳細，具有一定的參考價值，感興趣的小伙伴們可以參考一下

本文為大家分享了java實現(xiàn)鏈表反轉(zhuǎn)的具體代碼，供大家參考，具體內(nèi)容如下

算法題：實現(xiàn)鏈表的反轉(zhuǎn)

提供了2種方法，迭代法、遞歸法。

（為了方便輸出可視化，在自定義的ListNode中重寫了toString方法。）

/**
 * Created By --- on 2021/8/12
 * 以下代碼可以直接粘貼進編譯器輸出
 */
public class ReverseList {
 
  public static void main(String[] args) {
    ListNode head = new ListNode(3, new ListNode(5, new ListNode(8, new ListNode(9))));
    System.out.println("初始鏈表：" + head);
 
    ListNode newList = reverseList(head);
    System.out.println("使用迭代法反轉(zhuǎn)鏈表：" + newList);
 
    ListNode newList2 = reverseList2(null, newList);
    System.out.println("使用遞歸法反轉(zhuǎn)鏈表：" + newList2);
  }
 
  /**
   * 迭代法
   */
  public static ListNode reverseList(ListNode head) {
    ListNode pre = null;
    ListNode cur = head;
    ListNode tmp;
    while (cur != null) {
      tmp = cur.next;
      cur.next = pre;
      pre = cur;
      cur = tmp;
    }
    return pre;
  }
 
  /**
   * 遞歸法
   */
  public static ListNode reverseList2(ListNode pre, ListNode cur) {
    if (cur == null) {
      return pre;
    }
 
    ListNode tmp = cur.next;
    cur.next = pre;
    pre = cur;
    cur = tmp;
    return reverseList2(pre, cur);
  }
 
 
}
 
 
/**
 * singly-linked list
 */
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() {
    StringBuilder sb = new StringBuilder(String.valueOf(val));
    ListNode next = this.next;
    while (next != null) {
      sb.append(next.val);
      next = next.next;
    }
    return sb.toString();
  }
}

輸出結(jié)果：

再為大家分享一段java實現(xiàn)鏈表反轉(zhuǎn)的三種方式

分別通過棧、遞歸、指針的方式實現(xiàn)：

import java.util.Stack;
 
public class ReverseLinkedList {
 
    public static void main(String[] args) {
        ReverseLinkedList reverseLinkedList = new ReverseLinkedList();
        reverseLinkedList.test();
    }
 
    public void test() {
        Node node1 = new Node(1);
        Node node2 = new Node(2);
        Node node3 = new Node(3);
        node1.setNext(node2);
        node2.setNext(node3);
        //方法需要替換
        node1 = reverseByPointer(node1);
        while (node1 != null) {
            System.out.println(node1.val);
            node1 = node1.getNext();
        }
    }
 
    //棧實現(xiàn)
    private Node reverseByStack(Node head) {
        if (head == null || head.getNext() == null) {
            return head;
        }
        Stack<Node> stack = new Stack<>();
        while (head != null) {
            stack.push(head);
            head = head.getNext();
        }
        head = stack.pop();
        Node tmp = head;
        while (!stack.empty()) {
            Node node = stack.pop();
            node.setNext(null);
            tmp.setNext(node);
            tmp = node;
        }
        return head;
    }
 
    //遞歸實現(xiàn)
    private Node reverseByRecursion(Node head) {
        if (head == null || head.getNext() == null) {
            return head;
        }
        //遞歸獲取當前節(jié)點的后一個節(jié)點
        Node tmp = reverseByRecursion(head.getNext());
        Node node = head.getNext();
        head.setNext(null);
        node.setNext(head);
        return tmp;
    }
 
    //指針實現(xiàn)
    private Node reverseByPointer(Node head) {
        if (head == null || head.getNext() == null) {
            return head;
        }
        //pre指針指向前一個節(jié)點，初始第一個節(jié)點的前節(jié)點為空
        Node pre = null;
        //tmp指針指向當前節(jié)點
        Node tmp = null;
        while (head != null) {
            //tmp指針指向head頭指針節(jié)點
            tmp = head;
            //head頭指針向后遍歷
            head = head.getNext();
            //反轉(zhuǎn)，設(shè)置當前節(jié)點的下一個節(jié)點為前一個節(jié)點
            tmp.setNext(pre);
            //pre指針向后移動，指向當前節(jié)點
            pre = tmp;
        }
        return tmp;
    }
 
    private class Node {
        private int val;
 
        private Node next;
 
        public Node(int val) {
            this.val = val;
        }
 
        public Node getNext() {
            return next;
        }
 
        public void setNext(Node next) {
            this.next = next;
        }
    }
}

以上就是本文的全部內(nèi)容，希望對大家的學(xué)習(xí)有所幫助，也希望大家多多支持腳本之家。

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