The penultimate node in the Java output linked list

Problem description

Input a linked list and output the penultimate node in the linked list. (the tail node is the last to last)

Nodes are defined as follows:

Idea 1:

First traverse the linked list and calculate its length; Then it is calculated that the penultimate node is the positive length - K + 1 Finally, traverse the linked list to find the node time complexity O (2n), which needs to traverse the linked list twice

The code is as follows:

Idea 2:

Look forward to traversing the linked list only once. Set two pointers, one to the first node and the second to the k-th node. Then the two pointers move backward synchronously. When the second pointer points to the tail node, the first pointer points to the penultimate node

code:

Idea 3:

Reverse the linked list, then the original problem becomes the k-th node of the positive number. However, this changes the original linked list and is not more efficient than idea 2

Linked list inversion: refer to Java language code example for implementing inverted linked list

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