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Gilbert Joseph Smith III

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• Difficulty: 2/5

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.

Useful Links

• Array.push()
• String.split()

Problem Script:

function pair(str) {
 return str;
}

pair("GCG");

Problem Explanation:

• You will get a DNA strand sequence and you need to get the pair and return it as a 2D array of the base pairs. Keep in mind that the provided strand should be first always.

Hint: 1

• There are two base case, A-T and C-G, these go both way. You can use regular expression, if statements of anything that you can think of.

Hint: 2

• I would recommend using a switch, as it makes things a lot smoother.

Hint: 3

• The result must be an array of arrays, so keep that in mind when pushing things.

Spoiler Alert!

Solution ahead!

Code Solution:

function pair(str) {
  // Return each strand as an array of two elements, the original and the pair.
  var paired = [];

  // Function to check with strand to pair.
  var search = function(char) {
    switch (char) {
      case 'A':
        paired.push(['A', 'T']);
        break;
      case 'T':
        paired.push(['T', 'A']);
        break;
      case 'C':
        paired.push(['C', 'G']);
        break;
      case 'G':
        paired.push(['G', 'C']);
        break;
    }
  };

  // Loops through the input and pair.
  console.log(char);
  for (var i = 0; i < str.length; i++) {
    search(str[i]);
  }

  return paired;
}

Code Explanation:

• The program is very simple, the best solution that I have come up with is to use a switch to catch all the possible four elements. Using if statements would take too much code. You could also use Regular Expressions.
• Since we have to the original and the pair, I decided to take all four cases instead of the base two.
• Create an empty array and use the search function to push the right values to the array and return them.