freeCodeCamp/dna-pairing.english.md at a68e3ef39d4958b1c5c933e3eb3a3c7799e00d15

Mo Zargham 437ba8b103 fix(curriculum): Read-search-ask link now point to correct url as noted in the issue (#37753 )

* fix: broken Read-search-ask link now point to correct url

* fix: changed link to original forum link with more views

* fix: changed http links to correct version

* fix: link in help modal

2019-11-19 19:54:48 -05:00

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id, title, isRequired, challengeType, forumTopicId

id	title	isRequired	challengeType	forumTopicId
afd15382cdfb22c9efe8b7de	DNA Pairing	true	5	16009

Description

The DNA strand is missing the pairing element. Take each character, get its pair, and return the results as a 2d array. Base pairs are a pair of AT and CG. Match the missing element to the provided character. Return the provided character as the first element in each array. For example, for the input GCG, return "G", "C"], ["C","G"],["G", "C" The character and its pair are paired up in an array, and all the arrays are grouped into one encapsulating array. Remember to use Read-Search-Ask if you get stuck. Try to pair program. Write your own code.

Instructions

Tests

tests:
  - text: <code>pairElement("ATCGA")</code> should return <code>[["A","T"],["T","A"],["C","G"],["G","C"],["A","T"]]</code>.
    testString: assert.deepEqual(pairElement("ATCGA"),[["A","T"],["T","A"],["C","G"],["G","C"],["A","T"]]);
  - text: <code>pairElement("TTGAG")</code> should return <code>[["T","A"],["T","A"],["G","C"],["A","T"],["G","C"]]</code>.
    testString: assert.deepEqual(pairElement("TTGAG"),[["T","A"],["T","A"],["G","C"],["A","T"],["G","C"]]);
  - text: <code>pairElement("CTCTA")</code> should return <code>[["C","G"],["T","A"],["C","G"],["T","A"],["A","T"]]</code>.
    testString: assert.deepEqual(pairElement("CTCTA"),[["C","G"],["T","A"],["C","G"],["T","A"],["A","T"]]);

Challenge Seed

function pairElement(str) {
  return str;
}

pairElement("GCG");

Solution

var lookup = Object.create(null);
lookup.A = 'T';
lookup.T = 'A';
lookup.C = 'G';
lookup.G = 'C';

function pairElement(str) {
 return str.split('').map(function(p) {return [p, lookup[p]];});
}

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