To delete a linked list using recursion, we can follow the following steps -
Create a recursive function to delete a node from the linked list. The function should take the head node of the linked list as a parameter.
Check if the head node is NULL, if it is, then return.
Call the recursive function with the next node of the head.
Delete the head node.
Here's the sample code to delete a linked list using recursion in C++:
void deleteList(Node* head)
{
if(head == NULL) return;
deleteList(head->next);
delete head;
}
This code first checks if the head is NULL, and if it is, the function returns. Otherwise, the function calls itself with the next node of the head, recursively deleting the entire list. Finally, the head node is deleted.
Note that while this code does delete the nodes of the linked list, it does not delete the memory used by the pointers to the nodes, so you will still need to delete the pointer to the head node separately after calling this function.
In the code I provided, the function deleteList() takes the head node of a linked list as a parameter. The function first checks if the head node is NULL. If it is, it means that the list is empty, and there are no nodes to delete, so the function simply returns.
If the head node is not NULL, the function calls itself recursively with the next node of the head by passing head->next as the parameter. This recursive call continues until the base case is reached, which is when the last node of the linked list is reached and its next pointer is NULL.
At this point, the function begins to backtrack through the call stack, deleting each node one by one. When the recursive call with head->next returns, the current head node is the last node before the NULL, so the function deletes it by calling delete head;.
The function continues to backtrack through the call stack, deleting each node until it has deleted all the nodes in the linked list.
It's important to note that when using recursion to delete a linked list, you should ensure that you have no other pointers to the nodes of the list, otherwise, you risk deleting nodes that are still being used elsewhere in your program, leading to undefined behavior.
Also, it's worth mentioning that while recursion can be a concise way to delete a linked list, it may not be the most efficient method, especially for large linked lists. In such cases, it may be more efficient to use a loop to iterate through the linked list and delete the nodes one by one.