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);
	}
}