Leetcode 147: “Insertion Sort List” Java Solution

In this Leetcode problem, we are sorting a singly-linked list using the “insertion sort” algorithm:

Given the head of a singly linked list, sort the list using insertion sort, and return the sorted list's head.

The steps of the insertion sort algorithm:

Insertion sort iterates, consuming one input element each repetition and growing a sorted output list.

At each iteration, insertion sort removes one element from the input data, finds the location it belongs within the sorted list and inserts it there.

It repeats until no input elements remain.

The following is a graphical example of the insertion sort algorithm. The partially sorted list (black) initially contains only the first element in the list. One element (red) is removed from the input data and inserted in-place into the sorted list with each iteration.

There are a couple of examples given:

Sorting examples

Singly linked lists

Singly linked lists are very useful data structures to know for code interviews. It is important to be familiar with them and comfortable solving elementary problems using them. In many cases, you won’t be allowed to simply write the list in an array, as it will defeat the purpose…