数据结构（二）之链表反转

一、链表反转

1、反转非递归算法

2、反转递归算法

链表结点：

package cn.edu.scau.mk;/**** @author MK* @param <T>*/
public class Node<T> {private T data;private Node<T> next = null;public Node(T data) {this.data = data;}public T getData() {return data;}public void setData(T data) {this.data = data;}public Node<T> getNext() {return next;}public void setNext(Node<T> next) {this.next = next;}}

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链表：

package cn.edu.scau.mk;import java.util.Comparator;/**** @author MK* @param <T>*/
public class LinkedList<T> {protected Node<T> head = null;/*** 添加** @param data*/public void add(T data) {//头结点为nullif (head == null) {head = new Node<>(data);return;}//寻找末结点Node<T> curNode = head;while (curNode.getNext() != null) {curNode = curNode.getNext();}curNode.setNext(new Node<>(data));//添加结点
    }/*** 删除** @param index 下标,从0开始* @return*/public boolean delete(int index) {//没有数据if (head == null) {return false;}//删除头结点if (index == 0) {head = head.getNext();}Node<T> curNode = head;int i = 1;while (curNode.getNext() != null) {if (i == index) {curNode.setNext(curNode.getNext().getNext());return true;}i++;curNode = curNode.getNext();}throw new IndexOutOfBoundsException("Index: "+index+", Size: "+i);}/*** 长度** @return*/public int length() {int len = 0;Node<T> curNode = head;while (curNode != null) {len++;curNode = curNode.getNext();}return len;}/*** 查找* @param index 位置* @return */public T get(int index) {Node<T> curNode = head;int i = 0;while (curNode != null) {if (i == index) {return curNode.getData();}i++;curNode = curNode.getNext();}throw new IndexOutOfBoundsException("Index: "+index+", Size: "+i);}/*** 排序* @param comparator 比较器*/public void sort(Comparator<T> comparator) {//没有数据if (head == null) {return;}Node<T> curNode = head;Node<T> nextNode;Node<T> minNode;while (curNode.getNext() != null) {minNode = curNode;  //默认最小结点为当前结点nextNode = curNode.getNext();  //下一个结点while (nextNode != null) {//比当前结点小，记录最小结点if(comparator.compare(curNode.getData(), nextNode.getData())>0){minNode=nextNode;}nextNode=nextNode.getNext();  //继续与下一个结点比较
            }//最小结点不是当前结点，交换数据if(minNode!=curNode){T data=curNode.getData();curNode.setData(minNode.getData());minNode.setData(data);}curNode=curNode.getNext();  //移至下一个结点
        }}/*** 打印输出*/public  void print() {Node<T> curNode = head;while (curNode!=null) {            System.out.print(curNode.getData()+" ");curNode=curNode.getNext();}System.out.println();}
}

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二、非递归算法

package cn.edu.scau.mk;/**** @author MK* @param <T>*/
public class ReverseLinkedList<T> extends LinkedList<T>{/*** 反转*/public void reverse() {//没有数据if (head == null) {return;}Node<T> curNode = head.getNext();Node<T> preNode = head;Node<T> nextNode;while (curNode != null) {nextNode = curNode.getNext();curNode.setNext(preNode);preNode = curNode;curNode = nextNode;}head.setNext(null);head = preNode;}
}

三、递归算法

package cn.edu.scau.mk;/**** @author MK* @param <T>*/
public class ReverseLinkedList<T> extends LinkedList<T>{/*** 递归反转*/public void reverse1() {head = reverseByCall(head);}/*** 递归函数* @param headNode 头结点* @return*/private Node reverseByCall(Node<T> headNode) {//没有数据if (headNode == null || headNode.getNext() == null) {return headNode;}Node<T> curNode = headNode.getNext();Node<T> rootNode = reverseByCall(curNode);curNode.setNext(headNode);headNode.setNext(null);return rootNode;}}