ESSENTIAL ARRAY PATTERNS 📌
Every Developer Should Know

1. TWO POINTERS

Find pairs, remove duplicates, compare elements
from both ends, and optimize array traversals.

2. SLIDING WINDOW

Solve subarray and contiguous sequence problems
efficiently without repeatedly recalculating values.

3. PREFIX SUM

Answer range-sum and cumulative queries quickly
by reusing previously computed sums.

4. KADANE'S ALGORITHM

Find the maximum-sum subarray in O(n) time.

5. BINARY SEARCH

Whenever the search space is sorted or monotonic,
think O(log n) instead of scanning everything.

6. CYCLIC SORT

Useful for finding missing, duplicate, or misplaced
numbers when values belong to a known range.

7. MERGE INTERVALS

Handle overlapping, merging, and scheduling
interval problems efficiently.

8. MONOTONIC STACK

Solve next greater/smaller element problems and
many range-optimization problems in O(n).

9. HASH MAP / FREQUENCY COUNT

Count occurrences, detect duplicates, and perform
fast lookups using hashing.

10. SORTING + GREEDY

Sort the data first, then make locally optimal
decisions to reach the best overall result.

✅ THE GOAL

Don't memorize individual solutions. Learn to recognize the pattern behind the problem.
Pattern recognition
→ Faster approach
→ Better complexity
→ Stronger interview performance