>>206
Rust

fn foo<'a, 'b>(input: &'b [&'a str]) -> Vec<Vec<&'a str>> {
 struct Data<'a> { name: &'a str, rep: usize, coll: Option<Vec<usize>>, }
 let mut data = Vec::<Data>::new();
 let mut map = HashMap::<&str, usize>::new();
 for s in input {
  let (index0, index1) = s.splitn(2, '=')
   .map(|s| match map.get(s) {
    Some(&index) => data[index].rep,
    None => {
     let index = data.len();
     map.insert(s, index);
     data.push(Data { name: s, rep: index, coll: Some(vec![index]), });
     index
    },
   })
   .sorted().tuple_windows().next().unwrap();
  if index0 != index1 {
   let coll0 = data[index0].coll.take().unwrap();
   let coll1 = data[index1].coll.take().unwrap();
   coll1.iter().for_each(|&index| data[index].rep = index0);
   data[index0].coll = Some(itertools::merge(coll0, coll1).collect());
  }
 }
 data.iter().map(|data| &data.coll).flatten()
  .map(|coll| coll.iter().map(|&index| data[index].name).collect()).collect()
}