Optimize away

Optimizing slow but correct C++ code

This is a hard coding problem that tests your ability to identify and eliminate performance bottlenecks in working code. You are given a correct implementation that solves its problem, but runs far slower than necessary—your task is to preserve correctness while dramatically improving speed.

Problems like this appear in trading and systems interviews because optimization requires deep understanding of data structures, memory layout, algorithmic complexity, and compiler behavior. Strong candidates profile the code mentally, spot the expensive operations (repeated allocations, cache misses, redundant traversals, or suboptimal algorithms), and refactor strategically. The challenge is not to rewrite from scratch, but to recognize where the original approach wastes cycles.

• Time and space complexity analysis
• Memory access patterns and cache efficiency
• Avoiding unnecessary allocations and copies
• Algorithm selection and loop optimization
• Early termination and pruning strategies