Custom Alphabet

https://lina.bitcron.com/post/code/2018-summer-fb-intern-mian-jing

Sort an input string using an arbitrary alphabetFor example: custom alphabet: xyzabcinput to sort according to custom alphabet: cyxzoutput according to custom alphabet: xyzc

//O(n)
 public String sortedStringWithCustomAlphabet(String s, String alphabet){
         if(s==null||alphabet==null)return null;
         Map<Character,Integer> map = new HashMap<Character,Integer>();
         for(int i = 0; i < s.length();i++){
             if(!map.containsKey(s.charAt(i))){
                 map.put(s.charAt(i),1);
             }else{
                 map.put(s.charAt(i),map.get(s.charAt(i))+1);
             }

         }
         StringBuilder sb = new StringBuilder(s.length());
         for(char c : alphabet.toCharArray()){           //扫描字母表排序
             if(!map.containsKey(c))continue;
             int t = map.get(c);
             while(t-->0){
             sb.append(c);
             }
         }
         return sb.toString();
     }