题解 | #找出字符串中第一个只出现一次的字符#

import java.util.Scanner;

// 使用indexOf和lastIndexOf快捷判断
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while (in.hasNextLine()) { 
            String s = in.nextLine();
            int length = s.length();
            String ans = "-1";
            for (int i = 0; i < length; i++) {
                char c = s.charAt(i);
                if (s.indexOf(c) == s.lastIndexOf(c)) {
                    ans = String.valueOf(c);
                    break;
                }
            }
            System.out.println(ans);
        }
    }
}