Company/Google

Problem Given a string s of '(' , ')' and lowercase English characters. Your task is to remove the minimum number of parentheses ( '(' or ')', in any positions ) so that the resulting parentheses string is valid and return any valid string. Formally, a parentheses string is valid if and only if: It is the empty string, contains only lowercase characters, or It can be written as AB (A concatenated with B), where A and B are valid strings, or It can be written as (A), where A is a valid string. Examples Example 1: ...

Problem Suppose we have a file system that stores both files and directories. An example of one system is represented in the following picture: ...

Problem Given a string, find the longest substring that contains only k unique or distinct characters. Examples Example 1: Input: S = "aabacbebebe", K = 3 Output: 7 Explanation: "cbebebe" is the longest substring with 3 distinct characters. Example 2: Input: S = "aaaa", K = 2 Output: -1 Explanation: There's no substring with 2 distinct characters. ...