https://www.techinterviewhandbook.org/grind75

1. Two Sum // 22.11.15
2. Valid Parentheses // 22.11.16
3. Merge Two Sorted Lists // 22.11.22
4. Best Time to Buy and Sell Stock // 22.11.25
5. Valid Palindrome // 22.11.29
6. Invert Binary Tree // 22.11.30