Update README file

Author: soapyigu

README.md

@@ -113,7 +113,7 @@
 [Shortest Distance to a Character](https://leetcode.com/problems/shortest-distance-to-a-character/)| [Swift](./String/ShortestDistanceToACharacter.swift)| Easy| O(n)| O(1)|
 [Multiply Strings](https://leetcode.com/problems/multiply-strings/)| [Swift](./String/MultiplyStrings.swift)| Medium| O(n)| O(1)|
 [Palindrome Permutation](https://leetcode.com/problems/palindrome-permutation/)| [Swift](./String/PalindromePermutation.swift)| Easy| O(n)| O(n)|
-[Valid Anagram](https://leetcode.com/problems/valid-anagram/)| [Swift](./String/ValidAnagram.swift)| Easy| O(nlogn)| O(1)|
+[Valid Anagram](https://leetcode.com/problems/valid-anagram/)| [Swift](./String/ValidAnagram.swift)| Easy| O(n)| O(n)|
 [Ransom Note](https://leetcode.com/problems/ransom-note/)| [Swift](./String/RansomNote.swift)| Easy| O(n)| O(n)|
 [Group Anagrams](https://leetcode.com/problems/anagrams/)| [Swift](./String/GroupAnagrams.swift)| Medium| O(nmlogm + nlogn)| O(n)
 [Find Duplicate File in System](https://leetcode.com/problems/find-duplicate-file-in-system/)| [Swift](./String/FindDuplicateFileInSystem.swift)| Medium| O(nm)| O(n)