I applied online. The process took 4 weeks.

The interview started with my interviewer (SDE - II) introducing himself and asking me to do the same. We then moved on to two LeetCode questions:

• Tree-based
• Permutation/Combination

Also, he asked about one of my projects that I mentioned in my introduction as 5 minutes were left.

At Amazon, our delivery route optimization often involves tree-like structures. Here's an interesting problem that reflects similar patterns:

Given a binary tree where:

• Each node contains a single digit (0-9)
• Each path from root to leaf represents a number

For example: path 4->2->1 represents number 421.

Write a function to compute the sum of all numbers represented by root-to-leaf paths.

Input: root - [1,2,3] 1 2 3 Output: 25

Input: root - [4,9,0,5,1] Output: 1026 4 9 0 5 1

Q2 - Amazon is developing a new word game where players rearrange letters within words while maintaining the structure of the phrase. The game has an interesting scoring system based on valid arrangements.

Game Rules:

1. Players receive a phrase where words are separated by single spaces
2. Players can shuffle letters within each word, but can't move letters between words
3. Word order must stay the same
4. The goal is to find all possible unique arrangements

For example, if a player gets the phrase "code jam":

• They can create "eocd maj" (valid - letters shuffled within each word)
• They cannot create "jam code" (invalid - word order changed)
• They cannot create "codj ame" (invalid - letters moved between words)

Challenge: You're part of the game development team, and you need to create a function that calculates how many different valid arrangements are possible for a given phrase. Since this number can be very large, return the result modulo 10^9 + 7. Can you help create an algorithm that counts all possible valid arrangements?