Trigger Words to Pattern Mapping

Question 1

What are the trigger words associated with substring/subarray problems?

Answer 1

• substring
• subarray
• contiguous

These words indicate the need to find contiguous sequences within a data structure.

Question 2

What pattern is commonly used for substring/subarray problems?

Answer 2

Sliding Window

This pattern helps in efficiently managing the current window of elements being considered.

Question 3

What data structures are used for finding duplicates/repeating?

Answer 3

• Set (for uniqueness)
• HashMap (for counting)

Sets allow for O(1) lookup to check for existing elements.

Question 4

What are the trigger words for sum problems?

Answer 4

• two sum
• three sum
• pair that sums

These phrases indicate the need to find pairs or groups of numbers that sum to a specific target.

Question 5

What pattern is used for valid/balanced problems?

Answer 5

Stack

The stack’s LIFO structure is suitable for matching opening and closing elements.

Question 6

What are the trigger words for counting/frequency problems?

Answer 6

• count frequency
• most frequent
• group by

These phrases indicate the need to analyze the frequency of elements.

Question 7

What data structure is commonly used for counting/frequency problems?

Answer 7

• HashMap
• Counter

The defaultdict or Counter from collections can simplify counting tasks.

Question 8

What are the trigger words for interval problems?

Answer 8

• intervals
• merge
• overlap

These words indicate the need to manage and manipulate ranges of values.

Question 9

What pattern is used for tree level/layer problems?

Answer 9

BFS

Breadth-First Search is effective for exploring tree levels.

Question 10

What approach is commonly used for tree path problems?

Answer 10

Recursion

This approach allows for depth-first traversal of tree paths.

Question 11

What are the trigger words for all combinations/permutations?

Answer 11

• all combinations
• all permutations
• all possible ways

These phrases indicate the need to generate all possible arrangements of elements.

Question 12

What pattern is used for finding in sorted arrays?

Answer 12

Binary Search

This pattern employs a divide and conquer strategy to efficiently locate elements.

Question 13

What are the trigger words for top K/Kth largest problems?

Answer 13

• top K
• Kth largest
• Kth smallest

These phrases indicate the need to find specific ranked elements within a dataset.

Question 14

What pattern is used for maximum/minimum subarray problems?

Answer 14

Kadane’s Algorithm or Sliding Window

These methods help in efficiently calculating maximum or minimum sums of contiguous subarrays.