65 lines
2.5 KiB
Markdown
65 lines
2.5 KiB
Markdown
# Binary
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Write a program that will convert a binary number, represented as a string (e.g. '101010'), to its decimal equivalent using first principles
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Implement binary to decimal conversion. Given a binary input
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string, your program should produce a decimal output. The
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program should handle invalid inputs.
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## Note
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- Implement the conversion yourself.
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Do not use something else to perform the conversion for you.
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## About Binary (Base-2)
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Decimal is a base-10 system.
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A number 23 in base 10 notation can be understood
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as a linear combination of powers of 10:
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- The rightmost digit gets multiplied by 10^0 = 1
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- The next number gets multiplied by 10^1 = 10
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- ...
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- The *n*th number gets multiplied by 10^*(n-1)*.
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- All these values are summed.
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So: `23 => 2*10^1 + 3*10^0 => 2*10 + 3*1 = 23 base 10`
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Binary is similar, but uses powers of 2 rather than powers of 10.
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So: `101 => 1*2^2 + 0*2^1 + 1*2^0 => 1*4 + 0*2 + 1*1 => 4 + 1 => 5 base 10`.
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## Getting Started
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Make sure you have read the [getting started with C++](http://help.exercism.io/getting-started-with-cpp.html)
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page on the [exercism help site](http://help.exercism.io/). This covers
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the basic information on setting up the development environment expected
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by the exercises.
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## Passing the Tests
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Get the first test compiling, linking and passing by following the [three
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rules of test-driven development](http://butunclebob.com/ArticleS.UncleBob.TheThreeRulesOfTdd).
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Create just enough structure by declaring namespaces, functions, classes,
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etc., to satisfy any compiler errors and get the test to fail. Then write
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just enough code to get the test to pass. Once you've done that,
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uncomment the next test by moving the following line past the next test.
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```C++
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#if defined(EXERCISM_RUN_ALL_TESTS)
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```
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This may result in compile errors as new constructs may be invoked that
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you haven't yet declared or defined. Again, fix the compile errors minimally
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to get a failing test, then change the code minimally to pass the test,
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refactor your implementation for readability and expressiveness and then
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go on to the next test.
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Try to use standard C++11 facilities in preference to writing your own
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low-level algorithms or facilities by hand. [CppReference](http://en.cppreference.com/)
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is a wiki reference to the C++ language and standard library. If you
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are new to C++, but have programmed in C, beware of
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[C traps and pitfalls](http://www.slideshare.net/LegalizeAdulthood/c-traps-and-pitfalls-for-c-programmers).
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## Source
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All of Computer Science [view source](http://www.wolframalpha.com/input/?i=binary&a=*C.binary-_*MathWorld-)
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