Distinct Subsequences 哥们总算自己写个自底向上的dp解

public class DistinctSubSeq {
	//long
    char[] cs;
    //short
    char[] ts;
    public int numDistinct(String S, String T) {
        cs=S.toCharArray();
        ts=T.toCharArray();
        int len1=cs.length-1;
        int len2=ts.length-1;
        int[][] l=new int[len2+1][len1+1];
        for(int j=0;j<cs.length;j++){
            char c=cs[len1-j];
            for(int i=0;i<ts.length;i++){
            	char m=ts[len2-i];
                if(m==c){
                    if(i==0&&j==0){
                        l[i][j]=1;
                        continue;    
                    }
                    if(i==0){
                        l[i][j]=l[i][j-1]+1;
                        continue;
                    }
                    if(j==0)
                        continue;
                    l[i][j]=l[i-1][j-1]+l[i][j-1];
                }else{
                    if(j==0)
                        continue;
                    l[i][j]=l[i][j-1];
                }
            }
        }
        return l[len2][len1];
    }
    public static void main(String[] args) {
    	DistinctSubSeq ds=new DistinctSubSeq();
    	int v=ds.numDistinct("ababcc", "abbc");
    	System.out.println(v);
	}
}

Code Rewrite:

int tlen,slen;
	    String s,t;
	    int res=0;
	    int[][] dp;
	    public int dp(){
	       int[]sum=new int[tlen];
	       dp=new int[slen+1][tlen+1];
	       for(int i=0;i<slen;i++){
	           char c=s.charAt(i);
	           for(int j=tlen-1;j>=0;j--){
	               char c2=t.charAt(j);
	               if(c==c2){
	                    if(j==0)
	                        dp[i][j]=1;
	                    else
	                        dp[i][j]=sum[j-1];
	                    sum[j]+=dp[i][j];
	               }
	           }
	       }
	       return sum[tlen-1];
	    }
	    public int numDistinct(String S, String T) {
	        if(T.length()>S.length())
	            return 0;
	        s=S;
	        t=T;
	        slen=s.length();
	        tlen=t.length();
	        return dp();
	    }