Question

I have an integer linked list of which both first half and second half are sorted independently.Now i need to merge two parts to create one single sorted linked list.

Sample input:

Input List 1: 1->2->3->4->5->1->2

Output : 1->1->2->2->3->4->5

Input List 2: 1->5->7->9->11->2->4->6

Output 2: 1->2->4->5->6->7->9->11

Expected output:

1,2,3…..

Answer 1

This is merge sort.

I will maintain two pointers:

ptr1 points to the first half’s first element

and ptr2 points to the second half’s first element.

you will need an extra array to store the final list, of course you can choose not to use this extra array, but that discussion is far away from the topic.

1, Compare *ptr1 and *ptr2, if *ptr1‘s value is smaller than *ptr2, then copy that value(i.e. *ptr1) to the final array, and let ptr1 move forward.

if ptr2‘s value is the smaller one, just copy *ptr2 and let ptr2 move forward

2, Stop when the pointer points after the last element, say if you have 5 elements in the first half a[0] a[1] a[2] a[3] a[4], then you should stop when the pointer points to
a[5]

3, If the first half is empty, then copy the rest of the second half, vice versa.