Grouping [mp]

Micro pattern¶

Description¶

Collect values sharing a level, canonical key, or derived property into one container.

Problems¶

Group by traversal level¶

Collect the current BFS frontier as a single group.

• 102. Binary Tree Level Order Traversal (Top Easy)
• 103. Binary Tree Zigzag Level Order Traversal (Top Medium)
• 329. Longest Increasing Path in a Matrix (Top Hard)
• 934. Shortest Bridge (Graph Theory)

Group by canonical key¶

Use a common representation as the grouping key.

• 49. Group Anagrams (Top Medium)

Group by frequency¶

Index the group containing a value by its occurrence count.

• 347. Top K Frequent Elements (Top Medium)

Group equal sweep coordinates¶

Apply all events at a coordinate before measuring its resulting state.

• 218. The Skyline Problem (Top Hard)

Group by assigned category¶

Preserve the internal order of each category before emitting categories in a separate order.

• 1203. Sort Items by Groups Respecting Dependencies (Graph Theory)