# Unique subsequence count

Focus on the count of endWith something

For example.

<https://leetcode.com/problems/number-of-unique-good-subsequences/>

In this question, we focus on the endWith0, endWith1, while iterating the string, we can update the endWithCount by

if c == '1'\
&#x20;   endWith1 = endWith0 + endWith1 + 1;  // 1 is to sequence with only '1' in the sequence\
if c =='0'\
&#x20;   endWith0 = endWith0 + endWith1;
