C++ Practice

Author: 31Sanskrati

Linked_list/Creation_Tranversal.cpp

@@ -1,6 +1,8 @@
 #include <iostream>
 using namespace std;
 
+//to create and print the linked list
+
 class node
 {
 public:

Linked_list/deletion.cpp

@@ -1,6 +1,8 @@
 #include <iostream>
 using namespace std;
 
+//to delete an element when an element is given to delete
+
 class node
 {
 public:

Linked_list/deletion_position.cpp

@@ -1,6 +1,8 @@
 #include <iostream>
 using namespace std;
 
+//To delete an element at a certain position
+
 class node
 {
 public:

Linked_list/inserting_node.cpp

@@ -1,6 +1,8 @@
 #include <iostream>
 using namespace std;
 
+//to insert a node in linked list
+
 class node
 {
 public:

Linked_list/length.cpp

@@ -0,0 +1,50 @@
+#include <iostream>
+using namespace std;
+
+//This program is for finding the length of linked list
+
+class node{
+    public:
+    int data;
+    node* next;
+};
+
+void push(node **head_ref, int new_data)
+{
+    node *new_node = new node();
+    new_node->data = new_data;
+    new_node->next = (*head_ref);
+    (*head_ref) = new_node;
+}
+
+//iterative method
+int count(node *head){
+    int count = 0;
+    node* current = head;
+    while(current != NULL){
+        count++;
+        current = current->next;
+    }
+    return count;
+}
+
+//recursive method
+int getcount(node* head){
+    if (head == NULL){
+        return 0;
+    }
+    else{
+        return 1+ getcount(head->next);
+    }
+}
+
+int main(){
+    node* head = NULL;
+    push(&head, 10);
+    push(&head, 5);
+    push(&head, 0);
+
+    cout<<count(head); //3
+    cout<<getcount(head); //3
+    return 0;
+}

Linked_list/reverse.cpp

@@ -0,0 +1,77 @@
+#include <iostream>
+using namespace std;
+
+//this program is to reverse linked list
+
+class node
+{
+public:
+    int data;
+    node *next;
+};
+
+void push(node **head_ref, int new_data)
+{
+    node *new_node = new node();
+    new_node->data = new_data;
+    new_node->next = (*head_ref);
+    (*head_ref) = new_node;
+}
+
+void printList(node *i)
+{
+    while (i != NULL)
+    {
+        cout << i->data << " ";
+        i = i->next;
+    }
+    cout<<endl;
+}
+
+//iterative method
+node* reverse(node* &head){
+    node* prevptr = NULL;
+    node* currptr = head;
+    node* nextptr;
+
+    while(currptr != NULL){
+        nextptr = currptr->next;
+        currptr->next = prevptr;
+
+        prevptr = currptr;
+        currptr = nextptr;
+    }
+    return prevptr;
+}
+
+//recursive method
+node* reverseRecursive(node* &head){
+    if(head == NULL || head->next==NULL){
+        return head;
+    }
+    node* newhead = reverseRecursive(head->next);
+    head->next->next = head;
+    head->next = NULL;
+
+    return newhead;
+}
+
+int main()
+{
+    node *head = NULL;
+    push(&head, 5);
+    push(&head, 4);
+    push(&head, 3);
+    push(&head, 2);
+    push(&head, 1);
+
+    printList(head); //1 2 3 4 5
+
+    node* newhead = reverse(head);
+    printList(newhead); // 5 4 3 2 1 
+
+    node* recurrsiveHead = reverseRecursive(newhead);
+    printList(recurrsiveHead); //1 2 3 4 5
+    
+    return 0;
+}

Linked_list/reverse_K_nodes.cpp

@@ -0,0 +1,62 @@
+#include <iostream>
+using namespace std;
+
+//this program is to reverse K nodes of linked list
+
+class node{
+    public:
+    int data;
+    node* next;
+};
+
+void printList(node* i){
+    while(i!=NULL){
+        cout<<i->data<<" ";
+        i = i->next;
+    }
+    cout<<endl;
+}
+
+void push(node** head, int new_data){
+    node* new_node = new node();
+    new_node->data = new_data;
+    new_node->next = *head;
+    *head = new_node;
+}
+
+node* reverseK(node* &head, int k){
+    node* prevptr = NULL;
+    node* currptr = head;
+    node* nextptr;
+
+    int count = 0;
+    while(currptr!=NULL && count<k){
+        nextptr = currptr->next;
+        currptr->next = prevptr;
+        prevptr = currptr;
+        currptr = nextptr;
+        count++;
+    }
+
+    if(nextptr!=NULL){
+
+    head->next = reverseK(nextptr, k);    
+    }
+    return prevptr;
+}
+
+int main(){
+    node *head = NULL;
+    push(&head, 5);
+    push(&head, 4);
+    push(&head, 3);
+    push(&head, 2);
+    push(&head, 1);
+
+    printList(head); // 1 2 3 4 5
+    int k = 3;
+    node* newhead = reverseK(head, k);
+    printList(newhead); // 3 2 1 5 4
+
+    return 0;
+}