Questions

Author: alisamad1

Linked_List/reverse_linked_list.cpp

@@ -1,23 +1,22 @@
-// we will be writing a code for reversing a linked list
-#include <iostream>
+#include<iostream>
 using namespace std;
 struct Node{
     int data;
-    Node* next;
-    Node(int val): data(val),next(nullptr) {}
+    Node * next;
+    Node(int val): data(val), next(nullptr){}
 };
-Node* reverseLinked(Node * head){
+Node * reverseLinkedList(Node * head){
     Node * curr = head;
     Node * prev = nullptr;
     while(curr != nullptr){
-        Node * next = curr->next;
+        Node *next = curr->next;
         curr->next = prev;
         prev = curr;
         curr = next;
     }
     return prev;
 }
-void printLinkedList(Node *head){
+void printList(Node * head){
     while(head){
         cout << head->data << " ";
         head = head->next;
@@ -30,10 +29,11 @@ int main(){
     head->next->next = new Node(3);
     head->next->next->next = new Node(4);
     head->next->next->next->next = new Node(5);
-    cout << "Original Linked List: "; 
-    printLinkedList(head);
-    head = reverseLinked(head);
-    cout << "Reversed Linked List: ";
-    printLinkedList(head);
+    head->next->next->next->next->next = new Node(6);
+    cout << "Original Linked List: " << endl;
+    printList(head);
+    head = reverseLinkedList(head);
+    cout << "Reversed Linked List: " << endl;
+    printList(head);
     return 0;
-}
+}

Linked_List/reverse_nodes_in_K_Groups.cpp

@@ -0,0 +1,61 @@
+// C++ Program to reverse the nodes of a linked list in k groups 
+// Leetcode number: 25 (Asked by Microsoft, Amazon, Facebook, etc.)
+#include<iostream>
+using namespace std;
+struct ListNode {
+    int data;
+    ListNode *next;
+    ListNode(int val) : data(val),next(nullptr) {}
+};
+int getLength(ListNode *head, int k){
+    int count = 0;
+    while(head != NULL){
+        count++;
+        head = head->next;
+    }
+    return count ;
+}
+ListNode* reverseKGroup(ListNode* head, int k){
+    if(head == NULL){
+        return NULL;
+    }
+    int length = getLength(head, k);
+    if(length < k){
+        return head;
+    }
+    ListNode* prev = NULL;
+    ListNode* curr = head;
+    ListNode* forward = NULL;
+    int count = 0;
+    while(curr != NULL && count < k){
+        forward = curr->next;
+        curr->next = prev;
+        prev = curr;
+        curr = forward;
+        count++;
+    }
+    head->next = reverseKGroup(forward,k);
+    return prev;
+}
+void printList(ListNode* head){
+    while(head){
+        cout << head->data <<" ";
+        head = head->next;
+    }
+    cout << endl;
+}
+int main(){
+    ListNode * head = new ListNode(1);
+    head->next = new ListNode(2);
+    head->next->next = new ListNode(3);
+    head->next->next->next = new ListNode(4);
+    head->next->next->next->next = new ListNode(5);
+    head->next->next->next->next->next = new ListNode(6);
+    cout << "Original Linked List: " << endl;
+    printList(head);
+    int k = 3;
+    head = reverseKGroup(head, k);
+    cout << "Reversed Linked List in K Groups: " << endl;
+    printList(head);
+    return 0;
+}