Update Important Questions.

Added three important questions with their links

Author: DebosmitaChatterjee24

Important Questions.

@@ -33,6 +33,9 @@
 - Find closest palindrome : https://leetcode.com/problems/find-the-closest-palindrome/
 - Remove Nth Node from End of the Linked List : https://leetcode.com/problems/remove-nth-node-from-end-of-list/
 - Two Sum : https://leetcode.com/problems/two-sum/
+- Valid Anagram : https://leetcode.com/problems/valid-anagram/
+- Group Anagrams : https://leetcode.com/problems/group-anagrams/
+- Search in Rotated Sorted Array : https://leetcode.com/problems/search-in-rotated-sorted-array/