[英]Removing a specific item from LinkedList in java without using any API
I am trying to remove an item from the LinkedList in java. 我正在尝试从Java中的LinkedList中删除一个项目。 This List is implemented by me and I am not using any java API.
该列表由我实现,我没有使用任何Java API。 The major trouble I am facing is with RECURSION as I am always lost in recursion coding.
我面临的主要麻烦是RECURSION,因为我总是在递归编码中迷路。
class List{
int N;
List next;
List current;
List(int N){
this.N =N;
this.next = null;
}
@Override
public String toString() {
String o = "";
List curr = this;
while(curr != null){
o += curr.N+"-->";
curr = curr.next;
}
return o+"TAIL";
}
}
Method implemented: 实现的方法:
private static List Remove(List L,int N){
if(L == null || L.next == null)
return L;
List current = L;
List previous = null;
while(current != null){
if(current.N == N){
current = current.next;
if(previous == null)previous = current;
else{
previous.next = current;
}
break;
}else{
previous = current;
current = current.next;
}
}
return previous;
}
Input - 输入-
List list1 = new List(1);
list1.next = new List(2);
list1.next.next = new List(3);
list1.next.next.next = new List(4);
list1.next.next.next.next = new List(5);
list1.next.next.next.next.next = new List(6);
list1.next.next.next.next.next.next = new List(7);
System.out.println("Before Removal "+list1.toString());
System.out.println("After Removal "+Remove(list1,3));
Output I am getting is - 我得到的输出是-
Here I am losing the value 1 as I am setting the current = current.next
or reference is being set to next value. 在这里,当我设置
current = current.next
或引用被设置为下一个值时,我将丢失值1。 So definitely I am having some problem with the presentation of data stored in different references. 因此,毫无疑问,我在存储存储在不同引用中的数据时遇到了一些问题。
The mistake is here: 错误在这里:
return previous;
You should return the original head of the list if it was not removed. 如果未删除列表,则应返回列表的原始标题。 To show it graphically:
以图形方式显示:
N == 3
List Before Removal: 1-->2-->3-->4-->5-->6-->7-->TAIL
At start of iteration 1:
L ^
previous (null)
current ^
No match -> iteration 2:
L ^
previous ^
current ^
No match -> iteration 3:
L ^
previous ^
current ^
Match -> remove current:
List After Removal: 1-->2-->4-->5-->6-->7-->TAIL
L ^
previous ^
current ^
At this point by returning previous
, you lose the former head element L
. 此时,通过返回
previous
,您将失去前一个头部元素L
For the case when the head element is to be removed, you should add a separate check before the loop. 对于要删除head元素的情况,应在循环之前添加单独的检查。
Btw your Remove
method is not recursive - it is never calling itself. 顺便说一句,您的
Remove
方法不是递归的-它永远不会自我调用。
It's simply because you are not returning the head - but instead the previous pointer to the node you just 'removed': 这仅仅是因为您没有返回头-而是指向您刚刚“删除”的节点的前一个指针:
static List Remove(final List L, final int N) {
// Base case for null head pointer
final List head = L;
if (head == null)
return head;
// Base case for removing the head
if (head.N == N)
return head.next;
List current = head.next;
List previous = head;
while (current != null) {
if (current.N == N) {
current = current.next;
if (previous == null) {
previous = current;
}
else {
previous.next = current;
}
break;
} else {
previous = current;
current = current.next;
}
}
return head;
}
Also - to clarify - this is not a recursive solution. 另外-要澄清-这不是递归解决方案。
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