[英]Merge Two Linked Lists using Java
Trying to figure out what I'm missing in my code that is supposed to merge linked list 2 to the end of linked list 1. Right now it's just getting the last element in the second list and returning that. 试图找出代码中我所缺失的内容,该内容应该将链表2合并到链表1的末尾。现在,它只是获取第二个列表中的最后一个元素并返回它。
The logic I was trying to use is walking down the first list (L1) and adding those elements one-by-one to new_list then doing the same for the second list (L2) after I've reached the end of L1. 我尝试使用的逻辑是沿着第一个列表(L1)向下移动,并将这些元素一个一个地添加到new_list中,然后在到达L1末尾后对第二个列表(L2)进行相同的操作。 I am also trying to avoid modifying L1 or L2, which is why I created a new_list.
我也试图避免修改L1或L2,这就是为什么我创建了一个new_list。
Any help would be greatly appreciated. 任何帮助将不胜感激。
public NodeList(int item, NodeList next) {
this.item = item;
this.next = next;
}
public static NodeList merge(NodeList l1, NodeList l2) {
NodeList new_list = new NodeList(l1.item, l1.next);
NodeList new_list2 = new NodeList(l2.item, l2.next);
while (true) {
if (new_list.next == null) {
if (new_list2.next == null) {
return new_list;
}
else {
new_list.next = new NodeList(new_list2.next.item, new_list2.next.next);
new_list2 = new_list2.next;
}
}
else {
new_list.next = new NodeList(new_list.next.item, new_list.next.next);
new_list = new_list.next;
}
}
}
You need to retain a reference to the first node in your list, which you do not do. 您需要保留对列表中第一个节点的引用,而不必这样做。 In the example below, I also break up your loop into two loops with predetermined termination conditions, since that is logically what you are trying to do.
在下面的示例中,我还将您的循环分成两个具有预定终止条件的循环,因为从逻辑上讲,这是您要尝试的操作。 Note that I never copy a reference to the existing list's elements, since you mentioned that you never want to modify them.
请注意,我从未复制对现有列表元素的引用,因为您提到您永远不想修改它们。 I do however increment the local reference to the inputs:
但是,我确实增加了对输入的本地引用:
public static NodeList merge(NodeList l1, NodeList l2) {
NodeList new_head = new NodeList(0, null);
NodeList new_node = new_head;
for(; l1 != null; l1 = l1.next) {
new_node.next = new NodeList(l1.item, null);
new_node = new_node.next;
}
for(; l2 != null; l2 = l2.next) {
new_node.next = new NodeList(l2.item, null);
new_node = new_node.next;
}
return new_head.next;
}
As you can see, this has a lot of code repetition, so it can easily be generalized for an arbitrary number of lists: 如您所见,这具有大量的代码重复,因此可以轻松地将其概括为任意数量的列表:
public static NodeList merge(NodeList... l) {
NodeList new_head = new NodeList(0, null);
NodeList new_node = new_head;
for(NodeList ln in l) {
for(; ln != null; ln = ln.next) {
new_node.next = new NodeList(ln.item, null);
new_node = new_node.next;
}
}
return new_head.next;
}
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