Leetcode•Jul 24, 2025
Sort Characters By Frequency
Hazrat Ali
Leetcode
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.
Example 1:
Input: s = "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: s = "cccaaa" Output: "aaaccc" Explanation: Both 'c' and 'a' appear three times, so both "cccaaa" and "aaaccc" are valid answers. Note that "cacaca" is incorrect, as the same characters must be together.
Example 3:
Input: s = "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
/**
*
* @param {string} s
* @return {string}
*/
const frequencySort = s => {
const map = {};
for (let c of s) {
map[c] = ~~map[c] + 1;
}
const bucket = Array(s.length + 1).fill('');
Object.keys(map).forEach(c => {
const count = map[c];
bucket[count] += c.repeat(count);
});
let result = '';
for (let i = bucket.length - 1; i > 0; i--) {
result += bucket[i];
}
return result;
};