remove-nth-node-from-end-of-list (#7)

Author: the1Riddle

C#/remove-nth-node-from-end-of-list.cs

@@ -0,0 +1,60 @@
+/**
+ * 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
+{
+    // Returns a ListNode
+    public ListNode RemoveNthFromEnd(ListNode head, int n)
+    {
+        ListNode dummy = new ListNode(-1);
+        dummy.next = head;
+        ListNode slow = dummy, fast = dummy;
+
+        for (int i = 0; i < n; i++)
+        {
+            fast = fast.next;
+        }
+
+        while (fast.next != null)
+        {
+            slow = slow.next;
+            fast = fast.next;
+        }
+
+        slow.next = slow.next.next;
+
+        return dummy.next;
+    }
+}
+
+/** SOLUTION TWO **/
+
+public class Solution {
+    public ListNode RemoveNthFromEnd(ListNode head, int n) {
+        ListNode current = head;
+        Dictionary<int, ListNode> nodePositions = new();
+
+        int i = 0;
+        while (current != null) {
+            nodePositions[i] = current;
+            current = current.next;
+            i++;
+        }
+
+        if (i - n == 0) {
+            return head.next;
+        }
+
+        nodePositions[i - n - 1].next = nodePositions[i - n].next;
+
+        return head;
+    }
+}