一、反向查找單鏈表

1、簡單查找

　　先遍歷獲取單鏈表單長度n，然后通過計算得到倒數(shù)第k個元素的下標為n-k，然后查找下標為n-k的元素。

2、優(yōu)化查找

? ? ? 先找到下標為k的元素為記錄點p1，然后設(shè)置新的記錄點p2的下標從0開始，同時遍歷兩個記錄點，直到p1的值為null，p2是倒數(shù)第k個元素。

單鏈表結(jié)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(jié)點為nullif (head == null) {head = new Node<>(data);return;}//尋找末結(jié)點Node<T> curNode = head;while (curNode.getNext() != null) {curNode = curNode.getNext();}curNode.setNext(new Node<>(data));//添加結(jié)點 }/*** 刪除** @param index 下標,從0開始* @return*/public boolean delete(int index) {//沒有數(shù)據(jù)if (head == null) {return false;}//刪除頭結(jié)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(shù)據(jù)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(jié)點為當(dāng)前結(jié)點nextNode = curNode.getNext(); //下一個結(jié)點while (nextNode != null) {//比當(dāng)前結(jié)點小，記錄最小結(jié)點if(comparator.compare(curNode.getData(), nextNode.getData())>0){minNode=nextNode;}nextNode=nextNode.getNext(); //繼續(xù)與下一個結(jié)點比較 }//最小結(jié)點不是當(dāng)前結(jié)點，交換數(shù)據(jù)if(minNode!=curNode){T data=curNode.getData();curNode.setData(minNode.getData());minNode.setData(data);}curNode=curNode.getNext(); //移至下一個結(jié)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

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二、簡單查找

package cn.edu.scau.mk;import java.util.HashMap;/**** @author MK* @param <T>*/ public class OpLinkedList<T> extends LinkedList<T> {/*** 簡單反向查找* @param index 倒數(shù)個數(shù)，從1開始* @return */public T getByLastIndex(int index) {//倒數(shù)個數(shù)小于1if (index < 1) {throw new IndexOutOfBoundsException("Last Index : " + index);}int len=this.length();//鏈表長度//倒數(shù)個數(shù)越界if (head == null||len<index) {throw new IndexOutOfBoundsException("Last Index: " + index + ", Size: " + 0);}len=len-index;//第n-k個Node<T> curNode = head; //默認第0個for (int i = 0; i < len; i++) { curNode = curNode.getNext();//第i+1個 }return curNode.getData();}}

?

三、優(yōu)化查找

package cn.edu.scau.mk;import java.util.HashMap;/**** @author MK* @param <T>*/ public class OpLinkedList<T> extends LinkedList<T> {/***優(yōu)化反向查找* @param index 倒數(shù)個數(shù)，從1開始* @return*/public T getByLastIndex(int index) {if (index < 1) {throw new IndexOutOfBoundsException("Last Index : " + index);}if (head == null) {throw new IndexOutOfBoundsException("Last Index: " + index + ", Size: " + 0);}//查找第index個結(jié)點Node<T> curNode = head;for (int i = 0; i < index; i++) {if (curNode==null) {throw new IndexOutOfBoundsException("Last Index: " + index + ", Size: " + i); }curNode = curNode.getNext();}//循環(huán)直到curNode為null，indexNode剛好為倒數(shù)index個 Node<T> indexNode = head;while (curNode != null) { curNode =curNode.getNext();indexNode=indexNode.getNext();}return indexNode.getData();} }

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