摘要： Invert a binary tree. 4 / \ 2 7 / \ / \1 3 6 9to 4 / \ 7 2 / \ / \9 6 3 1比较简单，二叉树里的题其实有点举一反三的意思，很多题会一道就差不多了。递归的反... 阅读全文

摘要： Write a SQL query to delete all duplicate email entries in a table named Person, keeping only unique emails based on its smallest Id.+----+-----------... 阅读全文

摘要： Find the contiguous subarray within an array (containing at least one number) which has the largest product.For example, given the array [2,3,-2,4], t... 阅读全文