# Overview

There are many recurring patterns in my programs.

On this page I explain in my own, non-scientific words, why and how I use them.

(TODO: write more, more, more on this page)

# Caching

The technique I probably use the most is *caching*:

Whenever a result needs to be computed multiple times and that computation took some time, then I store it in a cache.

Hereby *result* can be a number, a string or an object.
It is stored in a container and accessed via a unique key.

The *unique key* of an `std::vector`

or `std::map`

is its index.

Even though `std::map`

is much more flexible, I try to avoid it due to its lackluster performance compared
to `std::vector`

.

__Examples:__

- problem 9 (Special Pythagorean triplet)
- problem 14 (Longest Collatz sequence)
- problem 16 (Power digit sum)
- and many, many more ...

# Incremental computation

This is somehow related to caching:

if a program needs to compute multiple results then it's often more efficient to compute those in some order
such that we can re-use results from earlier iterations.

In my opinion, Dynamic Programming can be seen as the reversal of incremental computation.

__Examples:__

# Heatmap

green problems solve the original Project Euler problem and have a perfect score of 100% at Hackerrank, too.

yellow problems score less than 100% at Hackerrank (but still solve the original problem).

gray problems are already solved but I haven't published my solution yet.

blue problems are already solved and there wasn't a Hackerrank version of it (at the time I solved it) or I didn't care about it because it differed too much.

*Please click on a problem's number to open my solution to that problem:*

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