1+ #include < bits/stdc++.h>
2+ using namespace std ;
3+ 4+ class node {
5+ 6+ public:
7+ int value ;
8+ node* next ;
9+ 10+ node (int data){
11+ value = data;
12+ next = NULL ;
13+ }
14+ };
15+ 16+ // inserting at the head
17+ void insertAtHead ( node* &head, int val){ // take by reference as we have to change the value of head
18+ node* new_node = new node (val);
19+ new_node-> next = head ;
20+ head = new_node;
21+ }
22+ 23+ // inserting at the tail
24+ void insertAtTail (node* &head, int val){
25+ 26+ node* new_node = new node (val) ;
27+ node* temp = head;
28+ 29+ while (temp->next !=NULL ){
30+ temp = temp->next ;
31+ 32+ }
33+ // temp has reached last node
34+ temp->next = new_node; // already points to NULL by the constuctor
35+ 36+ }
37+ 38+ // to insert the kth node
39+ void insertAtPosition (node* head, int val, int pos){
40+ 41+ if (pos ==0 ) {
42+ insertAtHead ( head, val) ;
43+ return ;
44+ }
45+ 46+ node* new_node = new node (val) ;
47+ node* temp = head;
48+ int cur_pos = 0 ;
49+ 50+ while (cur_pos!=pos-1 ){
51+ temp = temp->next ;
52+ cur_pos++;
53+ }
54+ 55+ // temp is pointing to pos-1
56+ 57+ new_node->next = temp->next ;
58+ temp->next = new_node;
59+ 60+ }
61+ 62+ // to update at kth node
63+ void updateAtPosition (node* head, int val, int pos){
64+ 65+ node* temp = head;
66+ int curr_pos = 0 ;
67+ 68+ while (curr_pos!=pos){
69+ 70+ temp = temp->next ;
71+ curr_pos++; }
72+ 73+ temp->value = val;
74+ }
75+ 76+ // to delete at head
77+ void deleteAtHead (node* &head){
78+ 79+ node* temp = head;
80+ 81+ head = temp->next ;
82+ delete temp;
83+ }
84+ 85+ // to delete at the last
86+ void deleteAtTail (node* head){
87+ 88+ node* second_last = head;
89+ while (second_last->next ->next != NULL ){
90+ second_last= second_last->next ;
91+ }
92+ 93+ node* temp = second_last->next ;
94+ second_last->next = NULL ;
95+ 96+ delete temp;
97+ 98+ }
99+ 100+ // to print all the nodes
101+ void display (node* head){
102+ node* temp= head;
103+ 104+ while (temp!=NULL ){
105+ cout << temp->value << " ->"
106+ temp = temp->next ;
107+ }
108+ cout << " NULL"
109+ }
110+ 111+ // to delete at kth position
112+ void deleteAtPosition (node* &head, int pos){
113+ 114+ if (pos==0 ){
115+ deleteAtHead (head);
116+ return ;
117+ }
118+ 119+ node* prev = head;
120+ int curr_pos = 0 ;
121+ 122+ while (curr_pos!=pos-1 ){
123+ prev= prev->next ;
124+ curr_pos++;
125+ }
126+ node* temp = prev->next ;
127+ prev->next = prev->next ->next ;
128+ delete temp;
129+ 130+ }
131+ 132+ int main (){
133+ 134+ // node *n = new node(1);
135+ 136+ // cout << n->value << " " << n->next;
137+ 138+ node* head = NULL ; // empty linked list
139+ 140+ insertAtHead (head,2 );
141+ insertAtHead (head,1 );
142+ insertAtTail (head,4 );
143+ insertAtPosition (head,5 ,1 );
144+ 145+ display (head);
146+ 147+ updateAtPosition (head,7 ,1 );
148+ 149+ display (head);
150+ 151+ // deleteAtHead(head);
152+ // deleteAtTail(head);
153+ deleteAtPosition (head,2 ) ;
154+ 155+ display (head);
156+ 157+ 158+ return 0 ;
159+ }
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