题解 | #找出字符串中第一个只出现一次的字符#

import java.util.*;
import java.io.*;
public class Main {
    public static void main(String[] args) throws IOException{
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        char[] chars=br.readLine().toCharArray();
        Map<Character,Integer> map=new LinkedHashMap<Character,Integer>();
        for(char ch:chars){
            Integer num=map.get(ch);
            if(num==null){
                map.put(ch,1);
            }else{
                map.put(ch,num+1);
            }
        }
        Character res=null;
        for(Character key:map.keySet()){
            if(map.get(key)==1){
                res=key;
                break;
            }
        }
        System.out.println(res==null?"-1":res);
        br.close();
    }
}