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Delete keys in a Linked list using C++ program

Delete keys in a Linked list: Here, we are implementing a C++ program to delete keys from the linked list.
Submitted by Souvik Saha, on May 06, 2019

Given a linked list and a key element, we have to delete the node from the linked list.

Explanation and example:

    If a linked list is like : 1 → 2 → 3 → 4 → 5 → 6

    Case I: (key is not head)
    The key value is 4
    After deleting that node the linked list is:1 → 2 → 3 → 5 → 6
    
    Case II: (key is head)
    The key value is 1
    After deleting that node the linked list is: 2 → 3 → 5 → 6

Algorithm:

To solve the problem there are two conditions,

  1. If the key node is the head of the linked list then we delete the node and point the head pointer to next node.
  2. If the key is not the head pointer of the linked list then simply delete that node.

C++ implementation:

#include <bits/stdc++.h>
using namespace std;

struct node{
    int data;
    node* next;
};

//Create a new node
struct node* create_node(int x){
    struct node* temp= new node;
    temp->data=x;
    temp->next=NULL;
    return temp;
}

//Enter the node into the linked list
void push(node** head,int x){
    struct node* store=create_node(x);
    if(*head==NULL){
        *head =store;
        return;
    }
    struct node* temp=*head;
    while(temp->next){
        temp=temp->next;
    }
    temp->next=store;
}

//Delete the middle node from the linked list
void delete_node(node** head,int x){
    if((*head)->next==NULL){
        *head=NULL;
        return;
    }
    struct node* temp=*head;
    if(temp->data==x){
    	temp=temp->next;
    	*head=temp;
    	return;
    }
    while(temp){
    	if(temp->data==x){
    		temp->data=temp->next->data;
    		temp->next=temp->next->next;
    		break;
    	}
    	temp=temp->next;
    }
}

//Print the list
void print(node* head){
	struct node* temp=head;
	while(temp){
		cout<<temp->data<<" ";
		temp=temp->next;
	}
}

int main()
{
    struct node* l=NULL;
    push(&l,1);
    push(&l,2);
    push(&l,3);
    push(&l,4);
    push(&l,5);
    push(&l,6);
    cout<<"Before the delete operation"<<endl;
    print(l);
    delete_node(&l,2);
    cout<<"\nAfter the delete operation"<<endl;
    print(l);
	
    return 0;
}

Output

Before the delete operation
1 2 3 4 5 6
After the delete operation
1 3 4 5 6





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