> big O notation and runtime complexity doesn’t matter the majority of the time and you can solve most problems with arrays I have the exact opposite experienc

> big O notation and runtime complexity doesn’t matter the majority of the time and you can solve most problems with arrays I have the exact opposite experience. Software comes out best if you always ensure to use an approach with sensible runtime complexity, and only make trade-offs towards cache-friendly-worse-O implementations where you benchmarked thoroughly. Most cases where I encounter mega slow programs are because somebody put in something quadratic instead of using a simple, standard O(n logn) solution. Check out https://www.tumblr.com/accidentallyquadratic https://www.tumblr.com/accidentallyquadratic for many examples.