题目：

https://leetcode.com/problems/distinct-subsequences/?tab=Description

 

一般没有明显思路的情况下，都要想想DP，用下Divide-and-Conque

 

下面的思路很好，很清晰

https://discuss.leetcode.com/topic/9488/easy-to-understand-dp-in-java/2

 

一个矩阵，如果字符不一样，那就用左侧的；如果字符一样，那就左侧+上方的。

An example:S: [acdabefbc] and T: [ab]first we check with a:           *  *      S = [acdabefbc]mem[1] = [0111222222]then we check with ab:               *  * ]      S = [acdabefbc]mem[1] = [0111222222]mem[2] = [0000022244]