摘要：
Table holds the x coordinate of some points on x axis in a plane, which are all integers. Write a query to find the shortest distance between two poin 阅读全文
摘要：
There is a robot starting at position (0, 0), the origin, on a 2D plane. Given a sequence of its moves, judge if this robot ends up at (0, 0) after it 阅读全文
摘要：
There is a table A country is big if it has an area of bigger than 3 million square km or a population of more than 25 million. Write a SQL solution t 阅读全文