> the experienced coder should be able to knock off in 5 minutes An inexperienced one will knock off in 5 minutes. An experienced one will know that the code

> the experienced coder should be able to knock off in 5 minutes An inexperienced one will knock off in 5 minutes. An experienced one will know that the code you'll write in 5 minutes will be way too slow, by an order of magnitude slower than good library implementations. For UTF8 see this: https://github.com/CppCon/CppCon2018/blob/master/Presentations/fast_conversion_from_utf8_with_cpp_dfas_and_sse_intrinsics/fast_conversion_from_utf8_with_cpp_dfas_and_sse_intrinsics__bob_steagall__cppcon_2018.pdf https://github.com/CppCon/CppCon2018/blob/master/Presentatio... For bignums this: https://en.wikipedia.org/wiki/Intel_ADX https://en.wikipedia.org/wiki/Intel_ADX As you see, neither is solvable in 5 minutes. The examples in a neighbor comment are very good, BTW.