• Problem 19 ("Click-through balancing act" -- basic Python, pandas, and Numpy)
• Problem 20 ("Topic sentence extraction" -- SVD, Numpy, Python strings)
• Problem 21 ("Redlining" -- linear regression, Numpy, pandas, strings)
• Problem 17 (“Partitioning political blogs” — basic pandas + math to Numpy)
• Problem 18 (“Data jobs” — general Python + pandas)
• Problem 2 (“But her emails…” — SQL/pandas)
• Problem 4 (“DBSCAN” for clustering)
• Problem 8 (“triangle counting” — Numpy)
• Problem 12 (“snowball poem generator” — basic Python, strings)
• Problem 13 (“traveling salesperson” — basic Python)
• Problem 15 (“Semi-supervised learning” — math to Numpy)
• Problem 6 (“SQL parser” — string+regex)
• Problem 7 (“Olympics search trends” — SQL/pandas)
• Problem 5 (“JSON” — has one possibly tricky element)
• Problem 9 (“Board game similarity” — Numpy)
• Problem 11 (“Text preprocessing for ML” — strings, basic Python)
• Problem 14 (“Gaussian mixtures” — math to Numpy)