[英]Reversing single linked list
I tried to revert single linkied list as follows: 我尝试还原单个链接列表,如下所示:
public class MutableLst<T> {
public T current;
public MutableLst<T> next;
private MutableLst(T current){
this.current = current;
}
public static <T> MutableLst<T> create(T current){
return new MutableLst<T>(current);
}
public void reverse(){
MutableLst<T> newNext = null;
MutableLst<T> nxt = next;
next = newNext;
while(nxt != null) {
newNext = this; //<------- cycle is here
current = nxt.current;
next = newNext;
nxt = nxt.next;
}
}
But this implementation does not work. 但是此实现无效。 When I assign to
this
I got a cycle. 当我分配到
this
我有一个周期。 How to fix it? 如何解决?
You are reversing only the list, so I don't know why do you want to do something with "this" object. 您只反转列表,所以我不知道您为什么要对“ this”对象执行某些操作。 Anyway I think you should just use this: https://www.eclipse.org/collections/javadoc/7.0.0/org/eclipse/collections/api/list/MutableList.html#reverseThis--
无论如何,我认为您应该只使用它: https : //www.eclipse.org/collections/javadoc/7.0.0/org/eclipse/collections/api/list/MutableList.html#reverseThis--
I would use recursion, like this: 我将使用递归,如下所示:
public void reverse(MutableLst<T> previous){
if (this.current.next !== null) {
this.next.reverse(this);
}
this.next = previous;
}
public void reverse() {
reverse(null);
}
You will need to call reverse to the head of your list. 您将需要反向调用到列表的开头。 As about your concrete problem, you are changing the next before you get a chance to use it.
关于您的具体问题,在有机会使用它之前,您正在更改下一个。 You might want to do something like this instead:
您可能想要执行以下操作:
public void reverse(){
MutableLst<T> previous = null;
MutableLst<T> currentItem = this;
MutableLst<T> nxt = null;
while(currentItem != null) {
nxt = currentItem.next;
currentItem.next = previous;
previous = currentItem;
currentItem = nxt;
}
}
Your code's problem is that you never assign a value to next. 您的代码的问题是,您永远不会为next赋值。 Here's my iterative solution to your problem.
这是我对您的问题的迭代解决方案。 Also, to make it easier on yourself I would suggested having a head that references the beginning of your linked list.
另外,为了使自己更轻松,我建议您使用一个引用链接列表开头的标题。
public void reverse() {
MutableLst<T> prev = null;
MutableLst<T> curr = head;
MutableLst<T> next = null;
while (curr != null) {
next = curr.next;
curr.next = prev;
prev = curr;
curr = next;
}
}
head = prev;
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