I was interviewd by Arista Networks few days back.
Process -

Round 1 - Online Hackerrank challenge.
Given a string "_!helloworld5678234kjlm*&!", return alphanumeric string with groups of k.

Round 2 - Onsite
Questions -

1. Reverse string without any built-in library. Optimise it.
2. Implement stoi.
3. Find missing element in a running stream of integers. [No extra space]
4. Level order traversal in binary tree. [Non-recursive approach]

Round 3 - Onsite
Questions -

1. Inorder successor of node in BST.
2. Find all primes less than 'n'. [Used sieve of eratosthenes]
3. Really complex image representations are given in form of bits. They are represented in form of strings like "hello world" in 2-D arrays. Each character is an 8 bit grayscale pixel(black or white) that holds ASCII value of the character. Perform following operations -
   a. Decode the ASCII values of characters.
   b. Generate inverted representation of those characters.
   c. Invert the grayscale pixels using only bitwise operations.
   d. Check for palindrome on ASCII values.
4. Design Uber. [Lots of constraints added in this question]

Happy LeetCoding :)
Thanks!