Amazon Technical Code Challenges & Tips

1. Write a function to find the longest substring without repeating characters in a given string.

2. Implement a function that finds the median of two sorted arrays.

3. Given an array of integers, write a function to find the subarray with the maximum sum.

4. Implement a function to determine if a string is a valid palindrome considering only alphanumeric characters and ignoring case sensitivity.

5. Write an algorithm to perform a binary search on a sorted array and return the index of a target value.

6. Implement a function that returns the nth Fibonacci number using dynamic programming.

7. Given a binary tree, write a function to check if it is a valid binary search tree.

8. Write a function that generates all possible combinations of well-formed parentheses given `n` pairs of parentheses.

9. Implement a LRU (Least Recently Used) cache that supports `get` and `put` methods.

10. Write a function that takes a string and returns all the possible permutations of that string.