Union query set is a tree-shaped data structure, mainly used to solve some set merge query problems.
The combined search forest refers to storing the data collection in a tree structure, that is, each node stores the corresponding parent node. When the parent node itself means reaching the root node, the root node represents the collection.
#合查集Optimization
There are two optimization methods, namely merging by rank and path compression.
Combine by rank:
将较小的树合并的较大的树上，影响运算时间的树的深度，即此处的秩。
Path compression:
路径压缩即在原来的树的基础上，直接将原来的节点连接到根节点上，从而减少查找根的次数。
But no matter which method is used, the original structure of the tree will be changed and the original structure cannot be protected.