We have discussed doubly circular linked list introduction and its insertion.
Let us formulate the problem statement to understand the deletion process. Given a ‘key’, delete the first occurrence of this key in circular doubly linked list.
Case 1: Empty List(start = NULL)
- If the list is empty, simply return.
Case 2:List initially contain some nodes, start points to first node of the List
- If the list is not empty then we define two pointers curr and prev_1 and initialize the pointer curr points to first node of the list and prev_1 = NULL.
- Traverse the list using curr pointer to find the node to be deleted and before moving curr to next node, every time set prev_1 = curr.
- If the node is found, check if it is the only node in the list. If yes, set start = NULL and free the node pointing by curr.
- If the list has more than one node, check if it is the first node of the list. Condition to check this is (curr == start). If yes, then move prev_1 to the last node(prev_1 = start -> prev). After prev_1 reaches the last node, set start = start -> next and prev_1 -> next = start and start -> prev = prev_1. Free the node pointing by curr.
- If curr is not first node, we check if it is the last node in the list. Condition to check this is (curr -> next == start). If yes, set prev_1 -> next = start and start -> prev = prev_1. Free the node pointing by curr.
- If the node to be deleted is neither the first node nor the last node, declare one more pointer temp and initialize the pointer temp points to next of curr pointer (temp = curr->next). Now set, prev_1 -> next = temp and temp ->prev = prev_1. Free the node pointing by curr.
- If the given key(Say 4) matches with first node of the list(Step 4):
- If the given key(Say 8) matches with last node of the list(Step 5):
- If the given key(Say 6) matches with middle node of the list(Step 6):
List Before Deletion: 4 5 6 7 8 List doesn't have node with value = 9 List After Deletion: 4 5 6 7 8 List After Deleting 4: 5 6 7 8 List After Deleting 8: 5 6 7 List After Deleting 6: 5 7
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