Palantir Intern Software Engineer Interview Experience — One Coding Question on Summing Stock Prices by Day

Coding interview:

You're given stocks on different days where

input_data =
[ [("5/1", 200), ("5/5", 100), ("5/8", 50)]  # PLTR
  [("5/1", 50), ("5/8", 100)]                # MSFT
  [("5/5", 50), ("5/8", 200)] ]              # AMZN

Find the total sum of each day and use the previous values of each day if they are not included. For each day that a company does not have a price in, use the previous day's value to add to the sum so that the sum is always incrementing.

The result for input_data would be:

[("5/1", 300), ("5/5", 200), ("5/8", 350)]