Day 23: The Naughty-Nice Glitch

"Santa, we need to talk!" Snowball stammered, holding a stack of printouts that smelled vaguely of desperation.

Santa looked up, his patience thinner than Rudolph’s battery life. "What now?"

Bernard, the senior elf, didn’t mince words. "It’s the Naughty-Nice List system. Legacy code. Written in JavaScript."

Santa froze. "Not even TypeScript?"

Bernard shook his head. "Plain JavaScript. var everywhere. No types. No safety. It’s a dumpster fire. Someone even polyfilled Promise with copy-paste."

Santa slammed his mug down. "So Naughty kids get PS5s, and Nice kids get socks because JavaScript?"

Snowball nodded, sweating. "It’s worse, Santa. There’s no validation. The Nice List has a SELECT * injection, and someone added console.log("Merry Christmas, LOL"); in production!"

Santa pinched the bridge of his nose. "Rewriting it in Rust is our only hope. No globals, no runtime panics—safety guaranteed. Bernard, make it happen."

"But Santa," Bernard hesitated, "starting from scratch this late… it’s risky."

Santa leaned forward, eyes blazing. "Riskier than trusting JavaScript on Christmas Eve? I don’t care how late it is. Write it in Rust."

Your Mission

Implement a SantaList struct that uses a HashMap to store children’s names as keys and their behaviors (true for nice, false for naughty) as values.

Fields

The SantaList struct should have a single field:

  • records - a HashMap<String, bool> to store children’s names and behaviors.

Methods

The struct should have the following methods and associated functions:

  • new - Create a new SantaList instance.
  • add - Add a child's name and behavior to the list.
  • remove - Remove a child from the list.
  • get - Retrieve a child's behavior.
  • count - Count the number of nice and naughty children as a tuple (nice, naughty)
  • list_by_behavior - Retrieve a list of children based on their behavior as Vec<String>

Hints

If you’re unsure where to start, take a look at these tips:

Click to reveal hints!

  • Using HashMap: Import it with use std::collections::HashMap;. Use HashMap::new() to create an empty map.

  • Adding/Updating: Use insert(key, value) to add or update an entry.

  • Querying: Use get(key) to retrieve values. It returns an Option<bool>.

  • Removing: Use remove(key) to delete an entry and get its value if it exists.

  • Counting: Use values() with .filter() to count nice/naughty children: