Create 25-Reverse-Nodes-in-k-Group.cs

Author: ShrujanKotturi

Diff for: csharp/25-Reverse-Nodes-in-k-Group.cs

@@ -0,0 +1,58 @@
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public int val;
+ *     public ListNode next;
+ *     public ListNode(int val=0, ListNode next=null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+public class Solution
+{
+    public ListNode ReverseKGroup(ListNode head, int k)
+    {
+        var dummy = new ListNode(0, head);
+        var groupPrev = dummy;
+        var groupNext = dummy;
+
+        while (true)
+        {
+            var kth = getKth(groupPrev, k);
+            if (kth == null)
+                break;
+
+            groupNext = kth.next;
+
+            // reverse group
+            var prev = kth.next;
+            var curr = groupPrev.next;
+
+            while (curr != groupNext)
+            {
+                var temp = curr.next;
+                curr.next = prev;
+                prev = curr;
+                curr = temp;
+            }
+
+            var tmp = groupPrev.next;
+            groupPrev.next = kth;
+            groupPrev = tmp;
+        }
+
+        return dummy.next;
+    }
+
+    private ListNode getKth(ListNode curr, int k)
+    {
+        while (curr != null && k > 0)
+        {
+            curr = curr.next;
+            k -= 1;
+        }
+
+        return curr;
+    }
+}