LeetCode 386. Lexicographical Numbers

386. Lexicographical Numbers
Given an integer n, return 1 – n in lexicographical order.

For example, given 13, return: [1,10,11,12,13,2,3,4,5,6,7,8,9].

Please optimize your algorithm to use less time and space. The input size may be as large as 5,000,000.

题目大意:给一个整数n,将1-n所有数按照字典序排序~
分析:从1~9分别深度优先遍历,对于每一次遍历,继续深度优先它的10 * cur + i(i从1~9),只要符合范围的就将该数字cur放入result数组中~最后返回result即可~