Microsoft OA

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

没有想到要再存一个HashMap, appearance to character mapping

 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);
     }
 }