摘要：
Given a string s, a k duplicate removal consists of choosing k adjacent and equal letters from s and removing them causing the left and the right side 阅读全文
摘要：
Given a string s containing only three types of characters: '(', ')' and '*', return true if s is valid. The following rules define a valid string: An 阅读全文
摘要：
Given the root of a Binary Search Tree (BST), convert it to a Greater Tree such that every key of the original BST is changed to the original key plus 阅读全文