[英]trim() method for linked list
我有一個問題,我在互聯網上四處張望,但找不到示例。 但是,在Java中制作一個String trim()方法(除去前導/尾隨空白),我知道這的基本代碼是:
public LString trim(){
int i = this.size;
int j = 0;
int k = this.offset;
char[] arrayOfChar = this.data;
while ((j < i) && (arrayOfChar[(k + j)] <= ' '))
++j;
while ((j < i) && (arrayOfChar[(k + i - 1)] <= ' '))
--i;
return (((j > 0) || (i < this.size)) ? substring(j, i) : this);
}
但是,您將如何編寫同樣的方法但將其應用於鏈表? 更具體地說,是使用Node類的鏈表。
這是我做的...。如果這是錯誤的,請更正...我將包括與該問題有關的相關課程信息。
public class LString{
private Node front = null; //first val in list
private Node back; //last val in list
private int size = 0;
private int i;
private int offset;
public LString(){
//construct empty list
Node LString = new Node();
front = null;
}
.......//skip down some methods to this one
//returns new lstring that is slice of lstring
//contains an endIndex as well
public LString substring(int beginIndex, int endIndex){
Node current = this.front;
int size = 0;
while(current != null && size < beginIndex){
size++;
current = current.getNext();
}
front = new Node();
front.setData(current.getData());
Node ocurrent = front;
while(current != null && size < endIndex){
current = current.getNext();
Node curr2 = new Node();
curr2.setData(current.getData());
ocurrent.setNext(curr2);
ocurrent = curr2;
size++;
}
ocurrent.setNext(null); //set next val to null to term string
return this;
}
public LString trim(){
String lstr;
int i = this.size;
int m = this.offset;
int k = charAt(m);
Node current = front;
while(current != null){
current = current.getNext();
if(current.data > '\u0020'){
return this;
} else if(current.data < '\u0020'){
LString lstring = new LString(); //this worked!?
return lstring;
}
}
return this.substring(k, m+1);
}
................................................... .............
//My Node class:
public class Node{
public char data;
public Node next;
//constructors from page 956
public Node()
{
this('\0',null); //'\0' is null char for java
}
public Node(char initialData, Node initialNext)
{
data = initialData;
next = initialNext;
}
}
(如果您不熟悉節點類,那么它基本上只會創建一個單鏈接節點,用作鏈接列表類中數據之間的鏈接)
我從未見過任何示例或任何內容,因此我想向社區詢問。
假如說
您應該記住,在Java中未公開LinkedList的內部實現(請注意: java.util.LinkedList.Node具有私有訪問修飾符),所有修改都是通過迭代器和LinkedList本身的方法執行的。
實施將是:
public static void trim (LinkedList list){
if (list == null || list.size() == 0) return;
Object element = null;
ListIterator i = list.listIterator();
while (i.hasNext() && element == null) {
element = i.next();
if (element == null) {
i.remove();
}
}
element = null;
i = list.listIterator(list.size());
while (i.hasPrevious() && element == null) {
element = i.previous();
if (element == null) {
i.remove();
}
}
}
但是,如果您要通過練習通過鏈表重新實現可變字符串 (如果不是作為練習,那么就在此處停止並使用StringBuilder或StringBuffer ),那么,假設您使用雙鏈表實現它,它將像這樣:
編輯:我不好,您可以迭代到第一個非空元素並直接設置對它的引用,更新算法
- 獲取第一個元素
- 當獲取的元素為空時,接下來獲取
- 將head引用設置為最后一個提取的元素,將last提取元素的prev引用設置為null
- 獲取最后一個元素
- 當獲取的元素為空時,獲取先前的元素
- 將尾引用設置為最后一個獲取的元素,將最后提取的元素的下一個引用設置為null
UPDATE使用您提供的代碼嘗試執行以下操作(由於您使用的是單鏈接列表,因此與上述列表略有不同):
public void trim(){
//early out if empty
if (front == null || back==null) return;
Node current = front;
//looking for the first non-empty element
while(current != null && current.data<'\u0020' ){
current = current.next;
}
//left trim
this.front = current;
//looking for last non-empty element
while (current!=null&¤t.next!=null&¤t.next.data>'\u0020'){
current = current.next;
}
//right trim
this.back = current;
if (current!=null){
current.next = null;
}
}
假設您只想修剪LinkedList中的每個String,為什么不僅僅遍歷每個項目呢?
LinkedList<String> myNodes = new LinkedList<String>();
myNodes.add('This is a node ');
myNodes.add(' another node '));
for (String s : myNodes){
s.trim();
}
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