Singly Linked List Implementation in C++

Linked_List.cpp

#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using namespace std;

#define ff              first
#define ss              second
#define in              cin
#define out             cout
#define int             long long
#define pb              push_back
#define mp              make_pair
#define pii             pair<int,int>
#define vi              vector<int>
#define mii             map<int,int>
#define pqb             priority_queue<int>
#define pqs             priority_queue<int,vi,greater<int> >
#define setbits(x)      __builtin_popcountll(x)
#define zrobits(x)      __builtin_ctzll(x)
#define rep(i, n)       for(int i = 0; i < n; i++)
#define REP(i,a,b)      for(int i=a;i<b;i++)
#define rep1(i,b)       for(int i=1;i<=b;i++)
#define mod             1000000007
#define inf             1e18
#define ps(x,y)         fixed<<setprecision(y)<<x
#define mk(arr,n,type)  type *arr=new type[n];
#define w(x)            int x; cin>>x; while(x--)
mt19937                 rng(chrono::steady_clock::now().time_since_epoch().count());

typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> pbds;


void c_p_c()
{
	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#ifndef ONLINE_JUDGE
	freopen("input.txt", "r", stdin);
	freopen("output.txt", "w", stdout);
#endif
}


struct Node
{
	int data;
	struct Node * next;

};

void Linked_List_Traverse(struct Node *ptr)
{

	while (ptr != NULL)
	{
		cout << "Elements in Linked List: " << ptr -> data << "\n";
		ptr = ptr -> next;
	}



}



struct Node * insertAtFirst(struct Node *head, int data)
{
	struct Node * ptr = (struct Node *) malloc(sizeof(struct Node));
	ptr -> next = head;  //ptr.next ptr.data ptr
	ptr -> data = data;
	return ptr;
}

struct Node * insertAtIndex(struct Node *head, int data, int index)
{
	struct Node * ptr = (struct Node *) malloc(sizeof(struct Node));
	struct Node * p = head;
	int i = 0;
	while (i != index - 1)
	{
		p = p -> next; //p.next
		i++;
	}

	ptr -> data = data;
	ptr -> next = p -> next;
	p -> next = ptr;
	return head;
};


struct Node * insertAtEnd(struct Node *head, int data)
{

	struct Node *ptr = (struct Node*) malloc(sizeof(struct Node));
	struct Node *p = head;
	ptr -> data = data;
	while (p -> next != NULL)
	{

		p = p -> next;

	}

	p -> next = ptr;
	ptr -> next = NULL;
	return head;


};


struct Node * insertAfterNode(struct Node *head, struct Node *prevnode, int data)
{
	struct Node *ptr = (struct Node *) malloc(sizeof(struct Node));
	ptr -> data = data;
	ptr -> next = prevnode -> next;
	prevnode -> next = ptr;
	return head;

};


/*Deletion in a linked list*/

struct Node * del_FirstNode(struct Node *head)
{
	struct Node * ptr = head; // ptr = head
	head = head -> next;
	free(ptr);
	return head;

};


struct Node * del_AtIndex(struct Node *head, int index)
{
	struct Node * p = head;
	struct Node * q = head -> next;
	for (int i = 0; i < index - 1; i++)
	{
		/* code */
		p = p -> next;
		q = q -> next;
	}

	p -> next = q -> next;
	free(q);
	return head;



};

struct Node * del_AtLast(struct Node *head)
{

	struct Node * p = head;
	struct Node * q = head -> next;
	while (q -> next != NULL)
	{
		/* code */
		p = p -> next;
		q = q -> next;
	}

	p ->next = NULL;
	free(q);
	return head;


};

struct Node * del_thevalue(struct Node *head, int value)
{

	struct Node * p = head;
	struct Node * q = head -> next;
	while (q -> data != value && q -> next != NULL)
	{
		/* code */
		p = p -> next;
		q = q -> next;
	}

	if (q -> data == value)
	{
		/* code */
		p -> next = q -> next;
		free(q);
	}


	return head;


};













//int *ptr;

int32_t main()
{
	c_p_c();

	struct Node * head;
	struct Node * second;
	struct Node * third;
	struct Node * fourth;

	/*Allocating memory in heap*/
	head = (struct Node *) malloc(sizeof(struct Node));
	second = (struct Node *) malloc(sizeof(struct Node));
	third = (struct Node *) malloc(sizeof(struct Node));
	fourth = (struct Node *) malloc(sizeof(struct Node));


	/*Link first and second node*/
	head -> data = 7;
	head -> next = second;

	/*Link second and third*/
	second -> data = 5;
	second -> next = third;

	third -> data = 11;
	third -> next = fourth;

	fourth -> data = 16;
	fourth -> next = NULL;


	cout << "\nLinked list before Insertion:\n\n";
	Linked_List_Traverse(head);
	cout << "\n<-------------------------------->\n";
	cout << "\nLinked list after Insertion at first:\n\n";
	head = insertAtFirst(head, 3);
	Linked_List_Traverse(head);
	cout << "\n<-------------------------------->\n";
	cout << "\nLinked list after Insertion at Index:\n\n";
	head = insertAtIndex(head , 56, 3);
	Linked_List_Traverse(head);
	cout << "\n<-------------------------------->\n";
	cout << "\nLinked list after Insertion at End:\n\n";
	head = insertAtEnd(head, 122);
	Linked_List_Traverse(head);
	cout << "\n<-------------------------------->\n";
	cout << "\nLinked list after Insertion after a Node:\n\n";
	head = insertAfterNode(head, second, 199);
	Linked_List_Traverse(head);
	cout << "\n<-------------------------------->\n";
	cout << "\nLinked list before deletion:\n\n";
	Linked_List_Traverse(head);
	cout << "\n<-------------------------------->\n";
	cout << "\nLinked List after deletion of first Node:\n\n";
	head = del_FirstNode(head);
	Linked_List_Traverse(head);
	cout << "\n<-------------------------------->\n";
	cout << "\nLinked List after deletion of Index Node:\n\n";
	head = del_AtIndex(head, 3);
	Linked_List_Traverse(head);
	cout << "\n<-------------------------------->\n";
	cout << "\nLinked List after deletion of Last Node:\n\n";
	head = del_AtLast(head);
	Linked_List_Traverse(head);
	cout << "\n<-------------------------------->\n";
	cout << "\nLinked List after deletion of value:\n\n";
	head = del_thevalue(head, 11);
	Linked_List_Traverse(head);



	return 0;
}

output.txt

Linked list before Insertion:

Elements in Linked List: 7
Elements in Linked List: 5
Elements in Linked List: 11
Elements in Linked List: 16

<-------------------------------->

Linked list after Insertion at first:

Elements in Linked List: 3
Elements in Linked List: 7
Elements in Linked List: 5
Elements in Linked List: 11
Elements in Linked List: 16

<-------------------------------->

Linked list after Insertion at Index:

Elements in Linked List: 3
Elements in Linked List: 7
Elements in Linked List: 5
Elements in Linked List: 56
Elements in Linked List: 11
Elements in Linked List: 16

<-------------------------------->

Linked list after Insertion at End:

Elements in Linked List: 3
Elements in Linked List: 7
Elements in Linked List: 5
Elements in Linked List: 56
Elements in Linked List: 11
Elements in Linked List: 16
Elements in Linked List: 122

<-------------------------------->

Linked list after Insertion after a Node:

Elements in Linked List: 3
Elements in Linked List: 7
Elements in Linked List: 5
Elements in Linked List: 199
Elements in Linked List: 56
Elements in Linked List: 11
Elements in Linked List: 16
Elements in Linked List: 122

<-------------------------------->

Linked list before deletion:

Elements in Linked List: 3
Elements in Linked List: 7
Elements in Linked List: 5
Elements in Linked List: 199
Elements in Linked List: 56
Elements in Linked List: 11
Elements in Linked List: 16
Elements in Linked List: 122

<-------------------------------->

Linked List after deletion of first Node:

Elements in Linked List: 7
Elements in Linked List: 5
Elements in Linked List: 199
Elements in Linked List: 56
Elements in Linked List: 11
Elements in Linked List: 16
Elements in Linked List: 122

<-------------------------------->

Linked List after deletion of Index Node:

Elements in Linked List: 7
Elements in Linked List: 5
Elements in Linked List: 199
Elements in Linked List: 11
Elements in Linked List: 16
Elements in Linked List: 122

<-------------------------------->

Linked List after deletion of Last Node:

Elements in Linked List: 7
Elements in Linked List: 5
Elements in Linked List: 199
Elements in Linked List: 11
Elements in Linked List: 16

<-------------------------------->

Linked List after deletion of value:

Elements in Linked List: 7
Elements in Linked List: 5
Elements in Linked List: 199
Elements in Linked List: 16