P8697 [蓝桥杯 2019 国 C] 最长子序列
AC

import java.util.Scanner;
public class Main {public static void main(String[] args) {Scanner sc = new Scanner(System.in);String s1 = sc.nextLine();String s2 = sc.nextLine();char[] c1 = s1.toCharArray();char[] c2 = s2.toCharArray();int ans = 0;for(int i=0,j=0;i<c1.length&&j<c2.length;i++) {if(c1[i] == c2[j]) {j++;ans++;}}System.out.println(ans);}
}