Create RemoveNthNodeFromEndOfList.java

Author: 17tanya

LinkedList/RemoveNthNodeFromEndOfList.java

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+//LeetCode 19. Nth Node From End of List
+//Question - https://leetcode.com/problems/remove-nth-node-from-end-of-list/
+
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+class Solution {
+    public ListNode removeNthFromEnd(ListNode head, int n) {
+        //dummy is needed when the node to be deleted is the first node
+        //In this case, the fast pointer would point to null after completing the for loop
+        //As a result the while loop is not activated and slow remains at the dummy node.
+        ListNode dummy = new ListNode();
+        dummy.next = head;
+        ListNode fast = dummy;
+        ListNode slow = dummy;
+        
+        //Make the fast pointer point to a location just after the nth node to be deleted
+        for(int i = 1 ; i <= n + 1; i++){
+            fast = fast.next;
+        }
+        
+        while(fast != null){
+            fast = fast.next;
+            slow = slow.next;
+        }
+        
+        slow.next = slow.next.next;
+        return dummy.next;
+    }
+}