leetcode/docs/(welcome)/hash-table/451.mdx

---
title: LC-451
description: Sort Characters By Frequency
---

## Examples

| Input      | Output   |
| ---------- | -------- |
| `"tree"`   | `"eert"` |
| `"cccaaa"` | `"aaaccc"` |
| `"Aabb"`   | `"bbAa"` |

## Hints

<Accordion type="single">
  <AccordionItem  title="Constraints">
    Constraints:
     • `1 <= s.length <= 5 * 10^5`
     • `s` consists of uppercase and lowercase English letters and digits.
  </AccordionItem >
  <AccordionItem  title="Problem Statement">
    Given a string `s`, sort it in decreasing order based on the frequency of the characters.
    The frequency of a character is the number of times it appears in the string.
    Return the sorted string. If there are multiple answers, return any of them.
  </AccordionItem >
</Accordion>

## Solution

```js
/**
 * @param {string} s
 * @return {string}
 */

var frequencySort = function (s) {
  // Default for Hammer
  const freq = {};
  for (let c of s) freq[c] = (freq[c] || 0) + 1;

  // Problem Specific
  // Sort characters by descending frequency; same chars stay grouped
  return s
    .split("")
    .sort((a, b) => freq[b] - freq[a] || a.localeCompare(b))
    .join("");
};
```