62 lines
1.8 KiB
Markdown
62 lines
1.8 KiB
Markdown
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# Binary
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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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* * * *
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For installation and learning resources, refer to the
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[exercism help page](http://exercism.io/languages/ruby).
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For running the tests provided, you will need the Minitest gem. Open a
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terminal window and run the following command to install minitest:
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gem install minitest
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If you would like color output, you can `require 'minitest/pride'` in
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the test file, or note the alternative instruction, below, for running
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the test file.
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Run the tests from the exercise directory using the following command:
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ruby binary_test.rb
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To include color from the command line:
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ruby -r minitest/pride binary_test.rb
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## Source
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All of Computer Science [http://www.wolframalpha.com/input/?i=binary&a=*C.binary-_*MathWorld-](http://www.wolframalpha.com/input/?i=binary&a=*C.binary-_*MathWorld-)
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## Submitting Incomplete Solutions
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It's possible to submit an incomplete solution so you can see how others have completed the exercise.
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