Facebook | E5 | Bay area | Feb 2021 | Reject

The interview process and format of each interview, for example:

-Technical phone screen (45 min):

• https://leetcode.com/problems/minimum-window-substring/
• https://leetcode.com/problems/verifying-an-alien-dictionary/

-Virtual Onsite (4 rounds):

1. Coding
   • https://leetcode.com/problems/sort-list/ (but the main condition is, we don't have access to the constructor, you can't use an array or any other data structure all you can do is copying node)- I was trying to something like bubble sort but did not work out (bummer on the first round)
   • https://leetcode.com/problems/kth-largest-element-in-an-array/ (solution using quick-select)
2. Behavior
   • Don't remember the exact questions but more on project, conflict, disagreement kind of stuff
   • Coding: https://leetcode.com/problems/valid-parentheses/
3. Coding
   • https://leetcode.com/problems/minimum-remove-to-make-valid-parentheses/
   • https://leetcode.com/problems/sum-root-to-leaf-numbers/ ( i did not know this question is there on leetcode at that time)
     you have given a binary tree, you need to consider root to leaf as one number, make all numbers from the entire tree, and return the sum

	                        5
						/       \
					  4         9 
				    /  \       /   
				  1    3     7
				
				541 + 543 + 591 = 1675

I solved using BFS like how we do level order problem (https://leetcode.com/problems/binary-tree-level-order-traversal/), 
store 
queue =(root,root.val) initially in queue
after poping node from queue, if it has left child  add leftchid node along and append left child value to root.val and add them in queue
queue = (root.left, ((root.val*10)+root.left.val))
same for right child
add termination condition for leaf node, add number in result. Do sum at the end

4. System design
System localization (Say I am opening Instagram in the African region, I should see content in the local language, How this system work end to end. How the developer will incorporate this service during development). I suck this one. The interviewer did not help much during the requirement gathering.

My overall experience is good. I am happy that I was able to solved unseen questions in 15 min with test case.
I was heavily relying on Facebook onsite but things go south this time. Mainly rejected because of system design.

Please post your thought on System localization, how would you approach it