求两个串的最大公共子序列的长度

 1 public class CommonSubsequence {
 2 
 3     public static int f(String s1,String s2){
 4         
 5         if(s1.length()==0||s2.length()==0) return 0;
 6         
 7         if(s1.charAt(0)==s2.charAt(0)) 
 8             return f(s1.substring(1),s2.substring(1))+1;
 9         else
10             return Math.max(f(s1.substring(1),s2), f(s1,s2.substring(1)));
11         
12     }
13     
14     
15     public static void main(String[] args) {
16         int k =f("abc","xbacd");
17         System.out.println(k);
18     }
19 
20 }