Summary

Add methods to reserve, obtain, and shrink UnionFind capacity.

Motivation

As mentioned in proposal #729, some algorithms can dynamically generate new elements during execution. And in cases where a certain bound of their number may become known during execution, it would be nice to immediately reserve the necessary capacity to avoid unnecessary re-allocations.

Progress

• UnionFind::capacity
• UnionFind::with_capacity()
• UnionFind::reserve
• UnionFind::reserve_exact
• UnionFind::try_reserve
• UnionFind::try_reserve_exact
• UnionFind::shrink_to_fit
• UnionFind::shrink_to