19-Remove-Nth-Node-From-End-of-List Java Solution

java/19-Remove-Nth-Node-From-End-of-List.java

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+/**
+ * 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; }
+ * }
+ */
+
+//         Using Two Pointer Approach:
+//         Take a pointer second and put it at (n+1)th position from the beginning
+//         Take pointer first and move it forward till second reaches Last Node and second.next points to null
+//         At that point we would have reached the (n-1)th node from the end using the pointer first
+//         Unlink or Skip that node
+
+
+class Solution {
+    public ListNode removeNthFromEnd(ListNode head, int n) {
+
+        if (head == null || head.next == null) return null;
+
+        ListNode temp = new ListNode(0);
+        temp.next = head;
+        ListNode first = temp, second = temp;
+
+        while (n > 0) {
+            second = second.next;
+            n--;
+        }
+
+        while (second.next != null) {
+            second = second.next;
+            first = first.next;
+        }
+
+        first.next = first.next.next;
+        return temp.next;
+
+    }
+}