LintCode-不同的子序列

 1 public class Solution {
 2     public int num = 0;
 3     
 4     
 5     /**
 6      * @param word1 & word2: Two string.
 7      * @return: The minimum number of steps.
 8      */
 9      public int numDistinct(String S, String T) {
10             // write your code here
11             find(S,T,0,0);
12             return num;
13         }
14         
15         public void find(String S,String T,int index,int from){
16             if(index ==  T.length()){
17                 num++;
18                 return;
19             }
20             
21             for(int i=from;i<S.length();i++){
22                 
23                 if(S.charAt(i) == T.charAt(index))
24                     find(S,T,index+1,i+1);
25             }
26         }
27 }