Sparse Matrix
Domain: Data Structures
🎯 Motivation
When a matrix is mostly zeros — like a social graph of 7 billion people where each knows only 100 — storing every cell wastes memory. Sparse formats store only non-zero entries.
📋 Concrete Example
A 1000x1000 matrix with only 50 non-zero values. Instead of 1,000,000 cells, store 50 (row, col, value) triples. Huge memory savings.
🔗 Analogy
A mostly empty attendance sheet for a huge lecture hall. Instead of marking absent for all 500 empty seats, you only write down the 5 students who showed up.