Coding Challenge Practice - Question 59

The task is to compress repeating letters with count number given a string.

The boilerplate code:

function compress(str) {
  // your code here
}

If it's not a string, return ""

if(!str) return "";

Start from the beginning of the string, and look at each character one by one. Keep a counter that tracks how many times the current character repeats consecutively.

let result = "";
let count = 1;

If the next character is the same as the current one, increase the counter

for(let i=1; i <= str.length; i++) {
if(str[i] === str[i - 1] {
count++
}
}

If the next character is different, the current group has ended. So add the character to the result, then add the count only if it is repeated more than once

 else {
      result += str[i - 1];
      if(count > 1) result += count
      count = 1;
    }

The final code

function compress(str) {
  // your code here
  if(!str) return "";

  let result = "";
  let count = 1;

  for(let i=1; i <= str.length; i++) {
    if(str[i] === str[i-1]) {
      count++
    } else {
      result += str[i - 1];
      if(count > 1) result += count
      count = 1;
    }
  }
  return result;

That's all folks!