题解 | #找出字符串中第一个只出现一次的字符#

import java.util.*;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        scanner.useDelimiter("\n");
        while (scanner.hasNext()) {
            String S = scanner.next();
            int[] or = new int[128];
            Arrays.fill(or, S.length());
            for (int i = 0; i < S.length(); i++) {
                 if (or[S.charAt(i)]!=S.length()) {
                     or[S.charAt(i)]=S.length()+1;
                     continue;
                 }
                 or[S.charAt(i)]=i;
            }
            OptionalInt min = Arrays.stream(or).min();
            System.out.println(min.getAsInt() < S.length() ? S.charAt(min.getAsInt()) : "-1");
        }
    }
}