Given a string S consisting of N lowercase letters, return the minimum number of letters that must be deleted to obtain a word in which every letter occurs a unique number of times

 package UniqueCharacter;

 import java.util.HashMap;

 import java.util.Map;

 public class Solution {

     public static int charCountToDelete(String s) {

         HashMap<Character, Integer> map = new HashMap<>();

         for (char c : s.toCharArray()) {

             map.put(c, map.getOrDefault(c, 0) + 1);

         }

         int res = 0;

         HashMap<Integer, Character> intToCharMap = new HashMap<>();

         for (Map.Entry<Character, Integer> entry : map.entrySet()) {

             int value = entry.getValue();

             while (intToCharMap.containsKey(value)) {

                 res ++; // need to delete

                 value --;

             }

             intToCharMap.put(value, entry.getKey());

         }

         return res;

     }

     public static void main(String[] args) {

         int res = charCountToDelete("aaaabbbbcccdde");

         System.out.printf("result is %d\n", res);

         int res2 = charCountToDelete("aaaabbbb");

         System.out.printf("result is %d\n", res2);

         int res3 = charCountToDelete("aaaabbbccd");

         System.out.printf("result is %d\n", res3);

     }

 }