摘要：
内连接(INNER JOIN)： 分为三种 等值连接、自然连接、不等连接 外连接(OUTER JOIN)： 左外连接(LEFT OUTER JOIN或LEFT JOIN) 右外连接(RIGHT OUTER JOIN或RIGHT JOIN) 全外连接(FULL OUTER JOIN或FULL JOIN 阅读全文
摘要：
Given an array of integers, 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once. Find all the elements that appear twi 阅读全文