摘要：Given the root of a binary tree, return the preorder traversal of its nodes' values. Example 1: Input: root = [1,null,2,3] Output: [1,2,3] Example 2: 阅读全文

摘要：Given a string s consisting of words and spaces, return the length of the last word in the string. A word is a maximal substring consisting of non-spa 阅读全文