Meta Hacker Cup Qualification Round Editorial

Good morning!

As usual, written editorials are available in the solution section of all problems on the Hacker Cup site. I thought this post might also be useful to see what people thought of the problems.

A: Second Hands

• Problem Statement, with written editorial
• Solution Video

B1/B2: Second Friend

• B1 Problem Statement, with written editorial
• B2 Problem Statement
• Moderately Entertaining Solution Video

C1/C2: Second Meaning

• C1 Problem Statement, with written editorial
• C2 Problem Statement
• Solution Video

D: Second Flight

• Problem Statement, with written editorial
• Solution Video

So, what'd you think of the problems?