Lookup Optimization Resource

Lookup Optimization Resource - aloalgo

The most common use of hash maps is to turn O(n) lookups into O(1). Whenever you find yourself using nested loops to "find" something, consider if a hash map could eliminate the inner loop.

Build a lookup table once, then query it many times.

You have a nested loop where the inner loop searches for something
You're doing repeated lookups in a collection
You need to find pairs/complements that satisfy a condition
You're matching elements between two collections
The problem involves "finding if X exists"

Time: O(n²) → O(n)
Space: O(1) → O(n)

This is almost always a worthwhile trade-off in interviews, where time complexity is usually more important than space.

Was this helpful?

Study plan All problems

Resources Cheat Sheet DSA Glossary

Lookup Optimization

The Pattern

Common Applications

Two Sum Variations

Finding Complements

Index Lookups

Checking Existence in Reference

Precomputation Pattern

Graph Representation

When to Use This Pattern

Trade-offs

Company

Practice

Learn