Minimum Deletions to Make Character Frequencies Unique

A string s is called good if there are no two different characters in s that have the same frequency.
Given a string s, return the minimum number of characters you need to delete to make s good.

Example 1:

Input: s = "aaabbbcc"
Output: 2

Approach

Java

import java.util.HashSet;

public class MakeCharacterFrequenciesUnique {
    public static void main(String[] args) {
        String s = "aaabbbcc";
        System.out.println(minDeletions(s));
    }

    // function to count minimum
    // deletions to make the frequency of
    // each characters as unique
    static int minDeletions(String s) {
        int f[] = new int[26];
        for (int i = 0; i < s.length(); i++)
            f[s.charAt(i) - 'a']++;
        int cnt = 0;
        HashSet<Integer> st = new HashSet<Integer>();
        for (int i = 0; i < 26; i++) {
            if (f[i] > 0) {
                if (st.contains(f[i])) {
                    cnt++;
                    int x = f[i] - 1;
                    int len = st.size();
                    st.add(x);
                    while (x > 0 && st.size() == len) {

                        len = st.size();
                        x--;
                        st.add(x);

                        cnt++;
                    }
                } else
                    st.add(f[i]);
            }
        }
        return cnt;
    }
}

C++

#include <bits/stdc++.h>
using namespace std;

//function to count minimum
//deletions to make the frequency of
//each characters as unique
int minDeletions(string s) 
{
     int f[26]={0};
        for(int i=0;i<s.size();i++)
               f[s[i]-'a']++;
        int cnt=0;
        set<int> st;
        for(int i=0;i<26;i++)
        {
            if(f[i]>0)
             {
               if(st.find(f[i])!=st.end())
               {
                   cnt++;
                   int x=f[i]-1;
                   int len=st.size();
                   st.insert(x);
                   while(x>0&&st.size()==len)
                   {
                       
                       len=st.size();
                       x--;
                       st.insert(x);
                       
                       cnt++;
                   }
               }
              else
                  st.insert(f[i]);
             }
        }
      return cnt;
}
int main()
{
    string s = "aaabbbcc";
    cout<<minDeletions(s);
    return 0;
}