A valid parentheses string is either empty (""), "(" + A + ")", or A + B, where A and B are valid parentheses strings, and +represents string concatenation. For example, "", "()", "(())()", and …
问题描述 有效括号字符串为空 ("")."(" + A + ")" 或 A + B,其中 A 和 B 都是有效的括号字符串,+ 代表字符串的连接.例如,"","()","(())()" 和 "(()(()))" 都是有效的括号字符串. 如果有效字符串 S 非空,且不存在将其拆分为 S = A+B 的方法,我们称其为原语(primitive),其中 A 和 B 都是非空…
709. To Lower Case(Easy)# Implement function ToLowerCase() that has a string parameter str, and returns the same string in lowercase. Example 1: Input: "Hello" Output: "hello" Example 2: Input: "here" Output: "here"…