摘要： A sequence of numbers is called arithmetic if it consists of at least three elements and if the difference between any two consecutive elements is the 阅读全文

摘要： A frog is crossing a river. The river is divided into x units and at each unit there may or may not exist a stone. The frog can jump on a stone, but i 阅读全文

摘要： Given a string that contains only digits 0-9 and a target value, return all possibilities to add binary operators (not unary) +, -, or *between the di 阅读全文