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Error-correct text

Correct a single-letter typo in a fixed text.

Input: The paragraph below but with exactly one typo, where a single letter a-zA-Z is replaced by a different letter a-zA-Z. To be clear, the letter isn't replaced everywhere it appears, but just in that one place. For example, the first word "In" might become "IZ". Non-letter characters like spaces or punctuation cannot be affected.

Output: The paragraph exactly as below, without the typo. A trailing newline is OK.

In information theory and coding theory with applications in computer science and telecommunication, error detection and correction or error control are techniques that enable reliable delivery of digital data over unreliable communication channels. Many communication channels are subject to channel noise, and thus errors may be introduced during transmission from the source to a receiver. Error detection techniques allow detecting such errors, while error correction enables reconstruction of the original data in many cases.

TIO with text

The text is taken from the Wikipedia article Error detection and correction. But, your code may not fetch the text from Wikipedia or elsewhere, as per the standard loophole.

Any site-default string I/O is acceptable. Fewest bytes wins. Please check that your solution works for all 23001 possible inputs, if you're able to run that much.

Answer*

C (gcc), 125 bytes
==========

Note: my code includes 2 unprintable characters `\x0c` and `0円x01` in the string literal which aren't visible in the snippet.


 b,i,j,m,n;C(char*T){b=i=n=0;for(;i<10;b|=("N<Syr4Zd"[i]!=m)<<i++)for(m=j=0;T[j];n^=!i*T[j++])m^=(1&j>>i)*T[j];T[b]^=120^n;}

[Try it online!](https://tio.run/##dVRNb9NAEBXHWPyIIQiwG5M2iAPCcSVUOCABF3qipGi9O6k3Xe@G/WgbQX97mV3HaVoJKVKcNzNv3rwZh7@@4PzurilluSq7UlcnOW@ZPTgt/jS1rHV9VC2NzSs5nx1Vzd86H3@bf3@6sW9/iCfjM7l4VnfFfC4nkyKmdfWKCk7PVotKn9fP5AE9TiaLojuv89nL1fGxLA5S9PSsWZzXszdH57q6vcuy51JzFQTOnRdKNtP2eB@yUl88goQ0EcmiWDjweOOhhvFnDVKTkI55aTT4Fo3dANMCuBFEMiDX0rfA1mslecp0VEYp3Tp4tOC4RM0x1XlUSIEu6G1qCWitsSDQI09denprtz8p1mdwo701CphFouGtlr8DOpLAPKBmjUKwqGR6EPRwhaTMLEHIC@mZAsE8A0MoBL1LfKAFaHqtUbkpfGV6859gEuBCsyKB4M2AgzbSYdlP2QbXq3bQsQ00SIaQeBE4ChDBJu8s066TzkXypTVddBOcCZa8Il5G43CMY0zh0yOP9uZnSpnrIUS0LvB227uE61bSkIN/O097u1xsQMvyNmytXiYJxpJjenCMNtklM5hDNx1XWUajECR1XmR/slF/MQ0Tv7ZX00VFPCdahTqPYDGZFVU2IoSvN/mQWkKKUSAb0Y1BHnljUGqBN0R0VKWMsx22qO7j9IYAdX9YecVUQKp8PXvzrtpD5vAQGIpHh4fw0aDTrzxcG3vZH7IOSsWtWsbpfB1tj7PgMHqzIUW2I3M89tvq36Ut1ZfAL6XagPRgNH1TfSAzNtAyFzeaWkTBTK1b1qCXfK9PYpFLyPcmIROKdPhSByTrKWOwb88Wmjj9yxS7yipmnuysLqqBO@6gW@e9/7vw1o3Rmqbxy3zcn5s2fjgaFO/hhUgf91OPy/s9lPeu7hGmfiOLPlgNs/TrdkR7Ht1m9Ml2jT6Q0x6dd/FsOaJAMR1T9e3dPw "C (gcc) – Try It Online")

The `i`th character in the literal is the XOR of all the characters in the original text at positions whose `i`th bit is `1`. The program performs the same XOR on the modified text. The computed value will be different iff the modified character is in a position with `i`th bit `1`. This gives us all the bits of the modified character's position.

Finally, we modify the character such that the XOR of all characters is that of the original text(120).

If this is an answer to a challenge…

…Be sure to follow the challenge specification. However, please refrain from exploiting obvious loopholes. Answers abusing any of the standard loopholes are considered invalid. If you think a specification is unclear or underspecified, comment on the question instead.
…Try to optimize your score. For instance, answers to code-golf challenges should attempt to be as short as possible. You can always include a readable version of the code in addition to the competitive one. Explanations of your answer make it more interesting to read and are very much encouraged.
…Include a short header which indicates the language(s) of your code and its score, as defined by the challenge.

More generally…

…Please make sure to answer the question and provide sufficient detail.
…Avoid asking for help, clarification or responding to other answers (use comments instead).

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2

\$\begingroup\$ I was just thinking that the binary number magic trick I remember from when I was a child would make a good approach to this (if you haven't seen it, check out, for example, norsemathology.org/wiki/index.php?title=Binary_Cards ). But then I went online and saw that you already did it! I do like this method. \$\endgroup\$

Mitchell Spector
– Mitchell Spector

2020年03月18日 03:20:12 +00:00
Commented Mar 18, 2020 at 3:20

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