pub fn new(count: usize) -> DisjointSetForest {
        let parent: Vec<usize> = (0..count).collect();
        let tree_size = vec![1_usize; count];
        DisjointSetForest {
            count,
            parent,
            tree_size,
        }
    }
Constructs forest of singletons with count elements.
src/union_find.rs