Union Find Disjoint Set Data Structure in DSA C - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the main purpose of the Union Find Disjoint Set data structure?

It helps to keep track of elements divided into groups called sets, and quickly find which set an element belongs to or merge two sets.

beginner

Explain the 'find' operation in Union Find Disjoint Set.

The 'find' operation returns the representative or leader of the set that an element belongs to. It helps check if two elements are in the same set.

beginner

What does the 'union' operation do in the Union Find Disjoint Set?

The 'union' operation merges two different sets into one by connecting their leaders, so elements from both sets become part of the same group.

intermediate

Why is path compression important in the Union Find Disjoint Set?

Path compression makes the 'find' operation faster by making every node on the path point directly to the leader, reducing the tree height.

intermediate

What is the role of 'union by rank' or 'union by size' in Union Find?

It helps keep the tree shallow by always attaching the smaller tree under the root of the larger tree, improving efficiency of operations.

What does the 'find' operation return in a Union Find Disjoint Set?

A The leader or representative of the set

B The size of the set

C The number of sets

D The parent of the element

The 'find' operation returns the leader or representative of the set that the element belongs to.

What is the main goal of the 'union' operation?

A To delete an element from a set

B To split a set into two

C To find the size of a set

D To merge two sets into one

The 'union' operation merges two different sets into a single set.

Which technique helps speed up the 'find' operation by flattening the tree?

A Breadth-first search

B Union by size

C Path compression

D Depth-first search

Path compression flattens the tree by making nodes point directly to the leader, speeding up future 'find' operations.

What does 'union by rank' help to achieve?

A Keeps the tree balanced by attaching smaller tree under larger

B Deletes the smaller tree

C Finds the rank of an element

D Splits the set into ranks

'Union by rank' attaches the smaller tree under the larger tree to keep the tree shallow and efficient.

If two elements have the same leader, what does it mean?

A They belong to different sets

B They belong to the same set

C They are not connected

D They are the leaders themselves

If two elements share the same leader, they belong to the same set.

Describe how the Union Find Disjoint Set data structure works and why it is useful.

Think about grouping elements and checking if they belong together.

Explain the optimizations 'path compression' and 'union by rank' in Union Find and how they improve performance.

Consider how trees can become tall and how to keep them short.