keep going

amazon.cpp

@@ -243,8 +243,48 @@ public:
     }
 };
 
+// Reverse Nodes in k-Group
+// Example:
 
+// Given this linked list: 1->2->3->4->5
 
+// For k = 2, you should return: 2->1->4->3->5
+
+// For k = 3, you should return: 3->2->1->4->5
+// Given a linked list, reverse the nodes of a linked list k at a time and return its modified list.
+
+// k is a positive integer and is less than or equal to the length of the linked list. If the number of nodes is not a multiple of k then left-out nodes in the end should remain as it is.
+// Note:
+
+// Only constant extra memory is allowed.
+// You may not alter the values in the list's nodes, only nodes itself may be changed.
+
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode(int x) : val(x), next(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* reverseKGroup(ListNode* head, int k) {
+       ListNode* current = head;
+       ListNode* next = nullptr;
+       ListNode* prev = nullptr;
+       while(current && k){
+         k--;
+        next = current->next;
+        current->next = prev;
+        prev = current;
+        current = next;
+       }
+
+     head->next = next;
+     return prev;
+    }
+};