Distincet Subsequences.java

//http://blog.csdn.net/linhuanmars/article/details/23589057
    public int numDistinct(String S, String T) {
        if(T.length()==0)  
        {  
            return 1;  
        }  
        if(S.length()==0)  
            return 0;  
        int[] res = new int[T.length()+1];  
        res[0] = 1;  
        for(int i=0;i<S.length();i++)  
        {  
            for(int j=T.length()-1;j>=0;j--)  
            {  
                res[j+1] = (S.charAt(i)==T.charAt(j)?res[j]:0)+res[j+1];  
            }  
        }  
        return res[T.length()];  
    }