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' each appear once. So 'e' must appear before both 'r' and 't'. "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 grouped together.
Example 3:
Input: s = "Aabb"
Output: "bbAa"
Explanation: 'b' appears twice, while 'A' and 'a' each appear once. Note that 'A' and 'a' are treated as two different characters.
1 <= s.length <= 5 * 10⁵s consists of uppercase and lowercase English letters and digits.