Delete a Node from Linked List
You have been given a linked list of integers. Your task is to write a function that deletes a node from a given position, 'POS'.

Note :

Assume that the Indexing for the linked list always starts from 0. If the position is greater than or equal to the length of the linked list, you should return the same linked list without any change.

Illustration :

The following images depict how the deletion has been performed.

Image-I :

Image-II :

Input format :

The first line contains an Integer 'T' which denotes the number of test cases or queries to be run. Then the test cases follow. The first line of each test case or query contains the elements of the linked list separated by a single space. The second line of each test case contains the integer value of 'POS'. It denotes the position in the linked list from where the node has to be deleted.

Remember/Consider :

While specifying the list elements for input, -1 indicates the end of the singly linked list and hence, would never be a list element

Output format :

For each test case/query, print the resulting linked list of integers in a row, separated by a single space. Output for every test case will be printed in a separate line.

Note:

You are not required to print the output, it has already been taken care of. Just implement the function.

Constraints :

1

Question

Delete a Node from Linked List

You have been given a linked list of integers. Your task is to write a function that deletes a node from a given position, 'POS'.

Note :

Assume that the Indexing for the linked list always starts from 0.

If the position is greater than or equal to the length of the linked list, you should return the same linked list without any change.

Illustration :

The following images depict how the deletion has been performed.

Image-I :

Alt txt

Image-II :

Alt txt

Input format :

The first line contains an Integer 'T' which denotes the number of test cases or queries to be run. Then the test cases follow.

The first line of each test case or query contains the elements of the linked list separated by a single space. 

The second line of each test case contains the integer value of 'POS'. It denotes the position in the linked list from where the node has to be deleted.

Remember/Consider :

While specifying the list elements for input, -1 indicates the end of the singly linked list and hence, would never be a list element

Output format :

For each test case/query, print the resulting linked list of integers in a row, separated by a single space.

Output for every test case will be printed in a separate line.

Note:

You are not required to print the output, it has already been taken care of. Just implement the function.

Constraints :

1 <= T <= 10^2
0 <= N <= 10^5
POS >= 0

Time Limit: 1sec

Accepted Answer

Step 1 : I first applied the native approach to iterate and find the previous and next node and the delete the given node.
Step 2 : I was asked to optimize and since I know the optimization so I used the recursive approach.
Step 3 : The interviewer was impressed over this.

Accepted Answer

Recursive Approach

If HEAD is null, return null since we can’t delete anything from an empty list.
If the head’s DATA is equal to the element we want to remove, return the next node from the HEAD. Othewise go to step 3.
Use recursion on the head’s next node to get the HEAD of the modified list.
Assign the head’s next node to this newly returned HEAD and return the original HEAD.

Space Complexity: O(n)Explanation:

O(MIN(POS, N)), where 'POS' is the position of the node deleted and 'N' being the size of the Singly Linked List.

Since this is the space required due to the recursion stack.

Time Complexity: O(n)Explanation:

O(MIN(POS, N)), where 'POS' is the position of the node deleted and 'N' being the size of the Singly Linked List.

Since we visit each node exactly once in a single iteration.

Accepted Answer

Iterative Approach

If the HEAD is null, return null since you can’t delete anything from an empty list.
If the head’s DATA is equal to the element you want to remove, return the next node from the HEAD. Otherwise, go to step 3.
Iterate through the list until you reach the node that is one before the node you wish to delete. Let that node be ‘A’, the node to be deleted, ‘B’, and the node after it, C. If B is the last node, then C will be null.
Assign A’s next node to be C instead of B and return the HEAD of the original list.
5. If while iterating, you finished the linked list, then just return the original HEAD.

Space Complexity: O(1)Explanation:

O(1) because constant extra space is used.