Theory: https://www.geeksforgeeks.org/array-data-structure/

Question 1: 217. Contains Duplicates

Question 2: 242. Valid Anagram

Question 3: 1. Two Sum

Question 4: 49. Group Anagrams

Question 5: 347. Top K Frequent Elements

Question 6: 238. Product of Array Except Self

Question 7: 36. Valid Sudoku

Question 8: 128. Longest Consecutive Sequence