Issue resolved #686

Author: sumitdethe27

Linked List/Remove_nth_node_from_end.java

@@ -0,0 +1,73 @@
+/**
+  Problem :-Remove the nth node from end of the list
+  https://leetcode.com/problems/remove-nth-node-from-end-of-list/description/
+
+  Approach:- 
+  1. First find the length of the list and store it in a variable named 'len'.
+  2. Then traverse the list  (len-n)
+  3. Now you are one node behind the node that we have to remove.
+
+  4. Now set the current node's next to the next.next i.e temp.next=temp.next.next.
+
+    Time Complexity : O(N) 
+    we traverse the list for calculating its length and removing the node.Hence O(N).
+
+    Space Complexity : O(1)
+    No extra space is required
+
+    Note :- The code is well documented. So take a look.
+
+
+
+ */
+
+
+/**
+ * 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) {
+        if (head == null) return head;          // If the head is null, return the head itself
+        if (head.next == null) {                // If there is only one node in the list
+            if (n == 1) return null;            // If n is 1, remove the node and return null
+            return head;                        // Otherwise, return the head itself
+        }
+        
+        ListNode temp = head;                    // Create a temporary node pointing to the head
+
+        int len = size(head);                   // Get the length of the list
+        if (len - n == 0) {                  // If the node to be removed is the head itself
+            head = head.next;                    // Move the head to the next node
+            return head;
+        }
+        
+        len -= n;                   // Calculate the index of the previous node of the node to be removed
+        for (int i = 1; i < len; i++) {      // Traverse to the previous node so we can remove the next node
+            temp = temp.next;
+        }
+        
+        if (temp != null && temp.next != null) {     // If the previous node and the node to be removed exist
+            temp.next = temp.next.next;    // Point the previous node to the node after the one to be removed
+        }
+        
+        return head;  // Return the updated head
+    }
+    
+    int size(ListNode temp) {
+        ListNode s = temp;
+        int n = 0;
+        while (s != null) {  // Traverse the list to count the number of nodes
+            s = s.next;
+            n += 1;
+        }
+        return n;  // Return the size of the list
+    }
+}