一、查找單鏈表中間結點

1、簡單查找

　　先遍歷獲取單鏈表單長度n，然后通過計算得到中間結點為n/2，然后查找下標為n/2的元素。

2、優化查找

? ? ? 先設置記錄點fast、slow，下標均從0開始，fast走兩步，slow走一步，同時遍歷兩個記錄點，直到fast的值為null，slow是中間結點。

單鏈表結點：

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;}} View Code

?鏈表：

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) {//頭結點為nullif (head == null) {head = new Node<>(data);return;}//尋找末結點Node<T> curNode = head;while (curNode.getNext() != null) {curNode = curNode.getNext();}curNode.setNext(new Node<>(data));//添加結點 }/*** 刪除** @param index 下標,從0開始* @return*/public boolean delete(int index) {//沒有數據if (head == null) {return false;}//刪除頭結點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);}/*** 長度** @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 比較器*/public void sort(Comparator<T> comparator) {//沒有數據if (head == null) {return;}Node<T> curNode = head;Node<T> nextNode;Node<T> minNode;while (curNode.getNext() != null) {minNode = curNode; //默認最小結點為當前結點nextNode = curNode.getNext(); //下一個結點while (nextNode != null) {//比當前結點小，記錄最小結點if(comparator.compare(curNode.getData(), nextNode.getData())>0){minNode=nextNode;}nextNode=nextNode.getNext(); //繼續與下一個結點比較 }//最小結點不是當前結點，交換數據if(minNode!=curNode){T data=curNode.getData();curNode.setData(minNode.getData());minNode.setData(data);}curNode=curNode.getNext(); //移至下一個結點 }}/*** 打印輸出*/public void print() {Node<T> curNode = head;while (curNode!=null) { System.out.print(curNode.getData()+" ");curNode=curNode.getNext();}System.out.println();} } View Code

?

二、簡單查找

package cn.edu.scau.mk;/**** @author MK* @param <T>*/ public class MidLinkedList<T> extends LinkedList<T> {/*** 獲取中間結點** @return*/public T getMid() {if (head == null) {throw new NullPointerException("no middle element");}Node<T> curNode = head;int len=length()/2;for (int i = 0; i <len ; i++) {curNode=curNode.getNext();}return curNode.getData();} }

?

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三、優化查找

package cn.edu.scau.mk;/**** @author MK* @param <T>*/ public class MidLinkedList<T> extends LinkedList<T> {/*** 獲取中間結點** @return*/public T getMid() {//沒有數據if (head == null) {throw new NullPointerException("no middle element");}Node<T> fast = head;Node<T> slow = head;while (fast != null && fast.getNext() != null) {fast = fast.getNext().getNext();//快記錄點走兩步slow = slow.getNext(); //慢記錄點走一步 }return slow.getData();} }

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