摘要：Given an array of integers A with even length, return true if and only if it is possible to reorder it such that A[2 * i + 1] = 2 * A[2 * i] for every 阅读全文

摘要：In an alien language, surprisingly they also use english lowercase letters, but possibly in a different order. The order of the alphabet is some permu 阅读全文

摘要：Given a non-empty array of unique positive integers A, consider the following graph: There are A.length nodes, labelled A[0] to A[A.length - 1]; There 阅读全文

摘要：For a binary tree T, we can define a flip operation as follows: choose any node, and swap the left and right child subtrees. A binary tree X is flip e 阅读全文