chore(CPlusPlus): add reverse in groups of K (#1106)

algorithms/CPlusPlus/Linked-Lists/reverseInGroupsOfK.cpp

@@ -0,0 +1,79 @@
+// Description := Reverse a linkedlist in groups of size K .
+
+// Time and space complexity :-
+// Time Complexity = O(N) and Space Complexity = O(N)
+
+// Example :-
+// Input: 1->2->3->4->5->6->7->8->NULL, K = 3 
+// Output: 3->2->1->6->5->4->8->7->NULL 
+
+#include<bits/stdc++.h>
+using namespace std;
+
+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* node)
+{
+    while (node != NULL) {
+        cout << node->data << " ";
+        node = node->next;
+    }
+}
+
+Node* kReverse(Node* &head, int k) {
+  
+    // base case
+    if(head == NULL) {
+        return NULL;
+    }
+    
+    Node* next = NULL;
+    Node* curr = head;
+    Node* prev = NULL;
+    int count= 0;
+    
+    while( curr != NULL && count < k ) {
+        next = curr -> next;
+        curr -> next = prev;
+        prev = curr;
+        curr = next;
+        count++;
+    }
+    
+    if(next != NULL) {
+        head -> next = kReverse(next,k);
+    }
+    return prev;
+}
+
+int main(){
+  Node* head=NULL;
+  Node* ans =head;
+  push(head,1);
+  push(head,2);
+  push(head,3);
+  push(head,4);
+  push(head,5);
+  push(head,6);
+  push(head,7);
+  push(head,8);
+  printList(head);
+  head = kReverse(head,3);
+  cout<<endl;
+  printList(head);
+}

algorithms/CPlusPlus/README.md

@@ -81,6 +81,7 @@
 - [Segregate Even Odd Nodes of linked list](Linked-Lists/segregate-even-odd-nodes-of-linked-list.cpp)
 - [Remove Duplicate in Sorted linked list](Linked-Lists/remove-duplicates-in-sorted-linked-list.cpp)
 - [Reverse the linked list using stack](Linked-Lists/reverse-the-list-using-stack.cpp)
+- [Reverse the linked list in groups of K](Linked-Lists/reverse-the-list-in-groups-of-k.cpp)
 ## Searching
 
 - [Linear Search](Searching/linear-search.cpp)