Question

In the following, you are given a given singly linked list. You are asked to save unique nodes in decreasing order of their frequency in the list. You cannot create new node in this or change values of existing nodes.

Sample input:
For example, you have this linked list.
L1: 2->100->12->5->6->5->2->1->5
If you run this function named L1.unique(). Then, L1.print() should display :
L1: 5->2->100->12->1->6

Answer 1

The student's question involves sorting nodes in a singly linked list by frequency without creating new nodes or changing node values, achievable through a combination of counting occurrences via a hash map and re-linking nodes.

Step-by-step explanation:

The question relates to the manipulation of data structures in computer programming, specifically managing a singly linked list. To sort the linked list nodes in decreasing order of their frequency without creating new nodes or changing existing node values, you would first need to count the occurrences of each value. The most common approach for this is to iterate through the list and use a hash map or dictionary to keep track of the counts of each value. Then, sort the nodes according to the recorded frequencies. It is important to note that you will have to manipulate the links between the nodes to reorder them in the desired frequency without altering node values.

For the sample input given (L1: 2->100->12->5->6->5->2->1->5), counting the occurrences yields the following frequencies: 5 occurs 3 times, 2 occurs twice, and all others occur once. The desired output after running L1.unique() would be a linked list ordered by frequencies: 5->2->100->12->1->6, since 5 has the highest frequency, followed by 2, and the rest have equal frequencies but are arranged in the order they appeared originally.