package com.github.wdn.coding2017.basic;
/**
* TODO 只是简单实现 缺少对边界的处理
* 参考JDK源码改为更优雅的实现
*/
public class LinkedList implements List {
private Node head;
private Node tail;
private int size;
public LinkedList(){
this.head=null;
this.tail=null;
}
public void add(Object o){
Node newNode = new Node(o);
if (head == null) {
head = newNode;
tail = newNode;
}else{
tail.setNext(newNode);
newNode.setPre(tail);
tail = newNode;
}
size++;
}
public void add(int index , Object o){
checkIndex(index);
Node indexNode = getNode(index);
Node newNode = new Node(o);
Node pre = indexNode.getPre();
if(pre!=null){
pre.setNext(newNode);
}else{
head = newNode;
}
newNode.setPre(pre);
newNode.setNext(indexNode);
indexNode.setPre(newNode);
size++;
}
private void checkIndex(int index){
if(index >= size || index <0){
throw new IndexOutOfBoundsException();
}
}
private Node getNode(int index){
checkIndex(index);
// TODO这里可以优化，先判断index在前半部还是后半部分 然后确定从头部或者尾部查找
Node result=null;
if(index==0){
return head;
}
if(index==size-1){
return tail;
}
Node current = head;
for (int i = 0; i < index; i++) {
result = current.getNext();
current = result;
}
return result;
}
public Object get(int index){
return getNode(index).getData();
}
public Object remove(int index){
checkIndex(index);
Node indexNode = getNode(index);
Node pre = indexNode.getPre();
Node next = indexNode.getNext();
if(pre!=null){
pre.setNext(next);
}else{
head = next;
}
if(next!=null){
next.setPre(pre);
}else{
tail = pre;
}
size--;
return indexNode.getData();
}
public int size(){
return size;
}
public void addFirst(Object o){
Node newNode = new Node(o);
if (size==0){
add(o);
return;
}
head.setPre(newNode);
newNode.setNext(head);
head = newNode;
size++;
}
public void addLast(Object o){
if (size == 0) {
add(o);
return;
}
Node newNode = new Node(o);
tail.setNext(newNode);
newNode.setPre(tail);
tail = newNode;
size++;
}
public Object removeFirst(){
if(size<1){
throw new IllegalArgumentException();
}
if(size==1){
tail=null;
}
Node next = head.getNext();
Node oldHead = head;
head.setPre(null);
head = next;
oldHead.setNext(null);
size--;
return oldHead;
}
public Object removeLast(){
if(size<1){
throw new IllegalArgumentException();
}
if(size==1){
head=null;
}
Node oldTail = tail;
Node pre = tail.getPre();
tail = pre;
tail.setNext(null);
oldTail.setPre(null);
size--;
return oldTail;
}
public Iterator iterator(){
return null;
}
/**
* JDK 中使用构造方法的方式设置next和pre减少不必要的getset方法更优雅
*/
private static class Node{
Object data;
Node next;
Node pre;
public Node(){
}
public Node(Object data){
this.data = data;
}
public Object getData() {
return data;
}
public void setData(Object data) {
this.data = data;
}
public Node getNext() {
return next;
}
public void setNext(Node next) {
this.next = next;
}
public Node getPre() {
return pre;
}
public void setPre(Node pre) {
this.pre = pre;
}
}
/**
* 把该链表逆置
* 例如链表为 3->7->10 , 逆置后变为 10->7->3
*/
public void reverse(){
Node current = head;
Node next = current.getNext();
Node pre = current.getPre();
while(next!=null){
Node nNext = next.getNext();
if(pre!=null){
pre.setPre(current);
}
if(current!=null){
current.setPre(next);
current.setNext(pre);
}
if(next!=null){
next.setNext(current);
}
pre = current;
current = next;
next = nNext;
}
Node oldHead = head;
head = tail;
tail = oldHead;
}
/**
* 删除一个单链表的前半部分
* 例如：list = 2->5->7->8 , 删除以后的值为 7->8
* 如果list = 2->5->7->8->10 ,删除以后的值为7,8,10
*/
public void removeFirstHalf(){
int removeSize = size/2;
for (int i = 0; i < removeSize; i++) {
removeFirst();
}
}
/**
* 从第i个元素开始， 删除length 个元素 ， 注意i从0开始
* @param start 开始位置
* @param length 长度
*/
public void remove(int start, int length){
checkIndex(start);
if(length<1){
return;
}
if(start==0 && length>=size){
int removeSum = size;
for (int j = 0; j < removeSum; j++) {
removeFirst();
}
size = size-length;
return;
}
int customMaxIndex = start+length;
int endIndex = customMaxIndex < size ? customMaxIndex : size;
if(start==0){
for (int j = 0; j < length; j++) {
removeFirst();
}
size = size-length;
return;
}
if(endIndex==size){
int removeSum = size-start;
for (int j = 0; j < removeSum; j++) {
removeLast();
}
return;
}
Node startNode = getNode(start-1);
Node endNode = getNode(endIndex);
startNode.getNext().setPre(null);
startNode.setNext(endNode);
endNode.getPre().setNext(null);
endNode.setPre(startNode);
size = size-length;
}
/**
* 假定当前链表和list均包含已升序排列的整数
* 从当前链表中取出那些list所指定的元素
* 例如当前链表 = 11->101->201->301->401->501->601->701
* listB = 1->3->4->6
* 返回的结果应该是[101,301,401,601]
* @param list
*/
public int[] getElements(LinkedList list){
for (int i = 0; i < list.size; i++) {
if(Integer.parseInt(list.get(i).toString())>=this.size){
throw new IndexOutOfBoundsException();
}
}
int[] result = new int[list.size];
int index = 0;
for (int i = 0; i < this.size; i++) {
if (index==list.size()){
break;
}
if(Integer.parseInt(list.get(index).toString())==i){
result[index] = Integer.parseInt(this.get(i).toString());
index++;
}
}
return result;
}
/**
* 已知链表中的元素以值递增有序排列，并以单链表作存储结构。
* 从当前链表中中删除在list中出现的元素
* @param list
*/
public void subtract(LinkedList list){
int index = 0;
Object compare = list.get(index);
Node current = head;
while(current!=null && compare!=null){
Node preCurrent = current;
current = current.getNext();
// TODO 这里不能删除重复元素只能删除一次
if(preCurrent.getData().equals(compare)){
preCurrent.getPre().setNext(preCurrent.getNext());
preCurrent.getNext().setPre(preCurrent.getPre());
preCurrent.setPre(null);
preCurrent.setNext(null);
size--;
compare = ++index < list.size ? list.get(index) : null;
}
}
}
/**
* 已知当前链表中的元素以值递增有序排列，并以单链表作存储结构。
* 删除表中所有值相同的多余元素（使得操作后的线性表中所有元素的值均不相同）
*/
public void removeDuplicateValues(){
Node current = head;
Node next = current.getNext();
while (next!=null){
if(next.getData().equals(current.getData())){
Node preNext = next;
next = preNext.getNext();
current.setNext(preNext.getNext());
if (next != null) {
next.setPre(current);
}
preNext.setPre(null);
preNext.setNext(null);
size--;
}else{
current = next;
next = next.getNext();
}
}
}
/**
* 已知链表中的元素以值递增有序排列，并以单链表作存储结构。
* 试写一高效的算法，删除表中所有值大于min且小于max的元素（若表中存在这样的元素）
* @param min
* @param max
*/
public void removeRange(int min, int max){
int minIndex = -1;
int maxIndex = -1;
int index = 0;
Node current = head;
while (current!=null){
if(current.getData().equals(min)){
minIndex = index;
}
if(current.getData().equals(max)){
maxIndex = index;
}
index++;
current = current.getNext();
}
if (minIndex > -1 && maxIndex > -1 && min <= max && minIndex + 1 < size) {
remove(minIndex + 1, maxIndex - minIndex - 1);
}
}
/**
* 假设当前链表和参数list指定的链表均以元素依值递增有序排列（同一表中的元素值各不相同）
* 现要求生成新链表C，其元素为当前链表和list中元素的交集，且表C中的元素有依值递增有序排列
* @param list
*/
public LinkedList intersection( LinkedList list){
return null;
}
@Override
public String toString(){
StringBuffer stringBuffer = new StringBuffer();
stringBuffer.append("[");
for (int i = 0; i < size; i++) {
stringBuffer.append(get(i));
if(i!=size-1){
stringBuffer.append(",");
}
}
stringBuffer.append("]");
return stringBuffer.toString();
}
}