Sort Characters By Frequency

Description

Given a string, sort it in decreasing order based on the frequency of characters.

Example 1:

Input:
"tree"
Output:
"eert"
Explanation:
'e' appears twice while 'r' and 't' both appear once.
So 'e' must appear before both 'r' and 't'. Therefore "eetr" is also a valid answer.

Example 2:

Input:
"cccaaa"
Output:
"cccaaa"
Explanation:
Both 'c' and 'a' appear three times, so "aaaccc" is also a valid answer.
Note that "cacaca" is incorrect, as the same characters must be together.

Example 3:

Input:
"Aabb"
Output:
"bbAa"
Explanation:
"bbaA" is also a valid answer, but "Aabb" is incorrect.
Note that 'A' and 'a' are treated as two different characters.

Solution(javascript)

const frequencySort = (s) => {
  const map = {}
  for (c of s) {
    if (map[c]) {
      map[c]++
    } else {
      map[c] = 1
    }
  }
  console.log(map)
  const toStr = (c, count) => {
    let current = c
    while (count > 1) {
      current += c
      count--
    }
    return current
  }
  return Object.keys(map)
    .sort((keyA, keyB) => map[keyB] - map[keyA])
    .map(key => toStr(key, map[key]))
    .join('')
}