Merge two sorted linked list

In this video, we will discuss three approaches to merge two sorted linked lists into one sorted linked list. The first approach uses an array. We start by extracting all the elements from both linked lists and storing them in an array. After sorting the array, we create a new linked list by sequentially inserting the sorted elements. This approach has a time complexity of O((n+m) * log(n+m)) due to the sorting operation, where n and m are the lengths of the two linked lists, and uses O(n+m) space for storing the elements in the array.

The second approach uses recursion to merge the two lists. In the base cases, if one of the lists is empty, we return the other list. For the recursive step, we compare the current nodes of both lists, attach the smaller node to the merged list, and recursively merge the remaining nodes. This approach efficiently merges the lists with a time complexity of O(n+m) and space complexity of O(n+m) due to the recursion stack.

The third and most efficient approach uses iteration to merge the lists. It eliminates the need for extra space used by recursion or arrays. By iteratively comparing the nodes of both lists, we can construct the merged list in a single pass. This approach also runs in O(n+m) time, but uses O(1) space as it does not require extra storage. Watch the video to understand the step-by-step process for each approach and how they efficiently merge two sorted linked lists.

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