# Delete all Occurrence of the key from the given linked list

“** Delete all Occurrence of the key from the given linked list**” is again one of the important problem asked in many technical interview based on linked list. Here, we are given a linked list and our task is to delete all occurrences of a given key ‘x’ from a linked list.

For example, we need to delete all occurrences of ‘45’ from a given list. List: 45 -> 55 -> 32 -> 45 -> 66 -> 71 -> 45 -> 33 -> 45 After deleting all occurrences of ‘45’, the list will become: List: 55 -> 32 -> 66 -> 71 -> 33

The steps required to Delete all Occurrence of the key from the given linked list is as follows:

- Before traversing the complete linked list, we will delete all beginning occurrences of given key ‘x’ and adjust our head accordingly.
- Now, after adjusting the head of the linked list, we will traverse the complete linked list and delete all occurrences of given key ‘x’ from a linked list.

**C++ Program to Delete all Occurrence of the key from the given linked list is as follows:**

/* C++ Program to delete all occurrences of the given key from the Linked List */ #include<bits/stdc++.h> using namespace std; /* Structure of the node of the linked list */ typedef struct node { int data; struct node *next; }Node; /* Function to Insert node at the end of the linked list */ void insert_end(Node **head, int ele) { /* Creating a new node */ Node *new_node; new_node = (struct node*)malloc(sizeof(struct node)); new_node->data = ele; new_node->next = NULL; /* check whether the linked list is empty or not */ /* If Linked List is empty, then new node will become head of the linked list */ if(*head == NULL) { *head = new_node; return; } /* If Linked List is not empty, then traverse the complete linked list and point the pointer of last node of the linked list to the new node */ Node *temp = NULL; temp = (*head); while(temp->next != NULL) temp=temp->next; temp->next = new_node; } /* Function to delete all occurrences of a given key from a linked list */ Node *deleteAllx(Node *head , int x) { /* If Linked List is empty, return head */ if(head == NULL) return head; /* Delete All occurrences of the given key from the beginning, and adjust head accordingly */ while(head!=NULL && head->data==x) head=head->next; /* Now, delete remaining occurrences of the key from the linked list by storing the previous node and pointing it to desired location accordingly */ Node* temp=head; while(temp->next != NULL) { if(temp->next->data == x) { Node *p = temp->next; temp->next=temp->next->next; delete p; } else { temp=temp->next; } } return head; } /* Function to Print the Linked List */ void print(Node *head) { Node *temp = head; while(temp!=NULL) { cout<<temp->data<<" "; temp=temp->next; } cout<<endl; } int main() { Node *head; head = NULL; /* Inserting Some Nodes in the Linked List */ insert_end(&head,45); insert_end(&head,78); insert_end(&head,45); insert_end(&head,93); insert_end(&head,45); insert_end(&head,99); insert_end(&head,45); cout<<"Linked List before deleting all occurrences of 45:\n"; print(head); head = deleteAllx(head,45); cout<<"\nLinked List after deleting all occurrences of 45:\n"; print(head); }

Linked List before deleting all occurrences of 45: 45 78 45 93 45 99 45 Linked List after deleting all occurrences of 45: 78 93 99OUTPUT:

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