摘要：
题目： The n-queens puzzle is the problem of placing n queens on an n×n chessboard such that no two queens attack each other. Given an integer n, return 阅读全文
摘要：
题目： Given a binary tree, return the postorder traversal of its nodes' values. Example: Follow up: Recursive solution is trivial, could you do it itera 阅读全文