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easyrust

Day 11: Santa's Snowy Algorithm

"LISTEN UP, YOU MAGNIFICENT, STRESSED-OUT CODERS!" Santa bellowed. "Tomorrow, we test the sleigh again. And this time, it WILL work. No more Florida nonsense. Palm trees are NOT part of the Christmas aesthetic."

He pointed dramatically at Bernard and Pepper. “You two are coming with me. If the sleigh glitches mid-flight again, I want live debugging happening in real time. No excuses.”

The elves whispered nervously. Everyone still remembered the "Florida Incident"—last week’s failed test landing in a snowless golf course. Santa didn’t appreciate the HOA complaints.

“This time,” Santa continued, pacing, “Snowball compiled every scrap of data we need for each location. Top-notch metrics. But metrics mean nothing without an algorithm. Your job is to write a function to find the snowball-densest landing spot.”

Your mission

Snowball has provided you with a Vec<Location>, now the other elves need to write a function to find the most dense area with snow.

Here is what you need to to:

  • Write a new() associated function for the Location struct that takes x: f64, y: f64, z: f64, area: f64, and snow.
  • The snow parameter must be able to accept all SnowKg, SnowLb and Snowball types.
  • Implement a method for the Location struct named density() that gets the density of snow in the location.
  • Finish the find_best_location function which takes a Vec<Location> and returns a Result<Location, Box<dyn Error>>.

That's it! 🎅

Hints

If you’re stuck or need a starting point, here are some hints to help you along the way!

Click here to show hints.

  • When we implemented the From<T> trait in the previous challenge, Rust automatically implemented the Into<T> trait for us. This means that if you implement From<T> for a type, you can convert that type to T using the into() method. e.g. let snow = snow.into();.

  • For the snow parameter, you can accept anything that implements the Into<Snowball> trait. e.g. new(x: f64, y: f64, z: f64, area: f64, snow: impl Into<Snowball>) -> Self. Here impl Into<Snowball> means any type that implements the Into<Snowball> trait.

  • Convert the snow parameter to a Snowball type using the into() method. e.g. let snow = snow.into();.

  • Implement the density() method for the Location struct. The density of snow is calculated by dividing the snow weight by the area of the location. Make sure you handle the division by zero case.

  • Use into_iter to convert the Vec<Location> to a consuming iterator. e.g. locations.into_iter().

  • Use the max_by() method to find the location with the highest density of snow. e.g.

    locations
  .into_iter()
  .max_by(|a, b| {
      a.density()
          .partial_cmp(&b.density())
          .unwrap_or(Ordering::Equal)
})

  • Import Ordering::Equal using use std::cmp::Ordering.

  • Use the ok_or() method to convert the Option returned by max_by() to a Result. e.g. ok_or("No locations found".into()).