Merge pull request #160 from Namanjain6152/rotate-a-linked-list

Rotate a linked list

Author: gantavyamalviya

CPP/Problems/rotate-linkedList/Namanjain6152.md

@@ -0,0 +1,50 @@
+<!-- reverse linked list logic iterative -->
+ListNode* reverse(ListNode* head){
+        if(!head||!head->next) return head;
+        ListNode* next=NULL, *curr=head, *prev= NULL;
+        while(curr){
+            next=curr->next;
+            curr->next=prev;
+            prev=curr;
+            curr=next;
+        }
+        return prev;
+    }
+    
+<!--rotate a linked list by k in right      -->
+ ListNode* rotateRight(ListNode* head, int k) {
+        if(!head||!head->next) return head;
+        ListNode* length= head;
+        int len=0;
+        while(length){
+            length=length->next;
+            len++;
+        }
+       
+        
+        ListNode* fast= head,*slow=head;
+        int val= k%len;
+        
+        while(fast&&val>0){
+            fast=fast->next;
+            val--;
+        }
+        if(fast==NULL){
+            return reverse(head);
+        }
+        while(fast->next!=NULL){
+            fast=fast->next;
+            slow=slow->next;
+        }
+        fast= slow->next;
+        slow->next=NULL;
+        slow=head;
+       ListNode* first= reverse(slow);
+      ListNode* second= reverse(fast);
+        ListNode* temp=first;
+        while(temp->next){
+            temp=temp->next;
+        }
+        temp->next= second;
+        return reverse(first);
+    }