Run Length

Question

Have the function RunLength(str) take the str parameter being passed and return a compressed version of the string using the Run-length encoding algorithm. This algorithm works by taking the occurrence of each repeating character and outputting that number along with a single character of the repeating sequence. For example: "wwwggopp" would return 3w2g1o2p. The string will not contain any numbers, punctuation, or symbols.

Solution

function RunLength(str) {
  // handle base case
  if (str.length === 1) {
    return `1${str}`;
  }

  // iterate through str, set current index and count number until change in char
  let res = '';
  let original = str.toLowerCase();
  let curLetter = original[0];
  let count = 1;
  for (let i = 1; i < original.length; i++) {
    if (original[i] === curLetter) {
      count++;
    } else {
      res += `${count}${curLetter}`;
      curLetter = original[i];
      count = 1;
    }

    // handle final letter
    if (i === original.length - 1) {
      res += `${count}${curLetter}`;
    }
  }

  // code goes here
  return res;
}
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