摘要：
题目描述 Given an integer n, count the total number of digit 1 appearing in all non-negative integers less than or equal to n. 题目大意 计算[0, n]之间的数字中包含多少1 。 阅读全文
摘要：
题目描述 Given a binary search tree, write a function kthSmallest to find the kth smallest element in it. Note: You may assume k is always valid, 1 ≤ k ≤ 阅读全文