Practice Problems
1. Easy Level​
- Ransom Note
- Isomorphic Strings
- Word Pattern
- Valid Anagram
- Two Sum
- Happy Number
- Contains Duplicate II
- Find the Difference of Two Arrays
- Unique Number of Occurrences
2. Medium Level​
- Group Anagrams
- Longest Consecutive Sequence
- Determine if Two Strings Are Close
- Equal Row and Column Pairs
3. Hard Level​
- Substring with Concatenation of All Words
- First Missing Positive
- Sudoku Solver
- Minimum Window Substring