DSA — Sets

What is a Set?

An unordered collection of unique elements.

# Creating sets
s = {1, 2, 3, 4, 5}
s = set([1, 2, 3, 4, 5])
s = set()  # Empty set

Set Operations

# Add
s.add(6)

# Remove
s.remove(3)
s.discard(10)  # No error if not found

# Membership
3 in s

# Size
len(s)

Set Mathematics

a = {1, 2, 3, 4}
b = {3, 4, 5, 6}

# Union
a | b  # {1, 2, 3, 4, 5, 6}

# Intersection
a & b  # {3, 4}

# Difference
a - b  # {1, 2}

# Symmetric Difference
a ^ b  # {1, 2, 5, 6}

Use Cases

# Remove duplicates
lst = [1, 2, 2, 3, 3, 3]
unique = list(set(lst))

# Fast membership testing
valid_ids = {101, 102, 103, 104}
if user_id in valid_ids:
    print("Valid")

Mini Practice

1. Create and manipulate sets
2. Perform set operations
3. Remove duplicates from a list
4. Find common elements

Up Next

Continue with Trees — tree data structure.