# Hamming

Calculate the Hamming difference between two DNA strands.

A mutation is simply a mistake that occurs during the creation or
copying of a nucleic acid, in particular DNA. Because nucleic acids are
vital to cellular functions, mutations tend to cause a ripple effect
throughout the cell. Although mutations are technically mistakes, a very
rare mutation may equip the cell with a beneficial attribute. In fact,
the macro effects of evolution are attributable by the accumulated
result of beneficial microscopic mutations over many generations.

The simplest and most common type of nucleic acid mutation is a point
mutation, which replaces one base with another at a single nucleotide.

By counting the number of differences between two homologous DNA strands
taken from different genomes with a common ancestor, we get a measure of
the minimum number of point mutations that could have occurred on the
evolutionary path between the two strands.

This is called the 'Hamming distance'.

It is found by comparing two DNA strands and counting how many of the
nucleotides are different from their equivalent in the other string.

    GAGCCTACTAACGGGAT
    CATCGTAATGACGGCCT
    ^ ^ ^  ^ ^    ^^

The Hamming distance between these two DNA strands is 7.

# Implementation notes

The Hamming distance is only defined for sequences of equal length. This means
that based on the definition, each language could deal with getting sequences
of equal length differently.

## Getting Started

Make sure you have read [the C++ page](http://exercism.io/languages/cpp) on
exercism.io.  This covers the basic information on setting up the development
environment expected by the exercises.

## Passing the Tests

Get the first test compiling, linking and passing by following the [three
rules of test-driven development](http://butunclebob.com/ArticleS.UncleBob.TheThreeRulesOfTdd).
Create just enough structure by declaring namespaces, functions, classes,
etc., to satisfy any compiler errors and get the test to fail.  Then write
just enough code to get the test to pass.  Once you've done that,
uncomment the next test by moving the following line past the next test.

```C++
#if defined(EXERCISM_RUN_ALL_TESTS)
```

This may result in compile errors as new constructs may be invoked that
you haven't yet declared or defined.  Again, fix the compile errors minimally
to get a failing test, then change the code minimally to pass the test,
refactor your implementation for readability and expressiveness and then
go on to the next test.

Try to use standard C++11 facilities in preference to writing your own
low-level algorithms or facilities by hand.  [CppReference](http://en.cppreference.com/)
is a wiki reference to the C++ language and standard library.  If you
are new to C++, but have programmed in C, beware of
[C traps and pitfalls](http://www.slideshare.net/LegalizeAdulthood/c-traps-and-pitfalls-for-c-programmers).

## Source

The Calculating Point Mutations problem at Rosalind [http://rosalind.info/problems/hamm/](http://rosalind.info/problems/hamm/)

## Submitting Incomplete Solutions
It's possible to submit an incomplete solution so you can see how others have completed the exercise.