How to Group Elements by Key in Rust (itertools group_by)

Use the itertools crate's group_by method on an iterator to collect consecutive elements sharing a key into sub-iterators. Add itertools to your Cargo.toml dependencies, import the trait, and chain .group_by() with a closure that extracts the grouping key.

use itertools::Itertools;

fn main() {
    let data = vec![1, 2, 2, 3, 3, 3];
    let grouped: Vec<_> = data.iter().group_by(|&x| x).into_iter().collect();
    println!("{:?}", grouped);
}

Add this to your Cargo.toml:

[dependencies]
itertools = "0.13"

Grouping elements by key in Rust organizes a list of items into buckets based on a shared characteristic, like sorting mixed coins into separate stacks for pennies, nickels, and dimes. This method works best when your data is already sorted by the key you want to group by. You use it when you need to process chunks of similar data together without writing complex loops.