text: /** 451. Sort Characters By Frequency
  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.
  
  **/
  
  #include <iostream>
  #include "../utils.h"
  using namespace std;
  
  class Solution {
  public:
      string frequencySort(string s) {
          
      }
  };
  
  int main() {
      Solution s;
      return 0;
  }
  