摘要：
Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses. For example, given n = 3, a solution set is: [ 阅读全文
摘要：
import java.util.Stack; /* * Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. An 阅读全文
摘要：
select t.request_at Day, ( round(count(if(status != 'completed', status, null)) / count(status), 2) ) as 'Cancellation Rate' from Users u inner join T 阅读全文