Sorting

Foundation

Learn the invariant, apply it independently, then pass the Sorting checkpoint.

• 3Sum (Medium)

Checkpoint

A graded check of the core Sorting reasoning skills.

Pattern Quest

Practice recognizing sorting problem shapes.

Sorting

Practice comparison invariants, partitioning, merging, heap order, custom tie-breakers, and sort-then-scan reductions that expose useful structure.

• Equal Sum Arrays with Minimum Number of Operations (Medium)
• Max Chunks To Make Sorted II (Hard)
• Minimum Deletions to Make Character Frequencies Unique (Medium)
• Sort Integers by The Power Value (Medium)
• The Number of Weak Characters in the Game (Medium)
• Top K Frequent Elements (Medium)