华为OD机考-字符串序列判定-双指针（JAVA 2025B卷）

public class Demo09 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while (in.hasNextLine()) {
            String S = in.nextLine();
            String L = in.nextLine();
            System.out.println(legal(S, L));
        }
        in.close();
    }


    public static int legal(String s, String l) {
        int preIndex = -1;
        for (int i = 0; i < s.length(); i++) {
            String c = String.valueOf(s.charAt(i));
            // 是否包含
            if (!l.contains(c)) {
                return -1;
            }
            int index = l.indexOf(c);
            // 顺序判断
            if (index > preIndex) {
                preIndex = index;
            } else {
                return -1;
            }
        }
        return preIndex;
    }
}