LeetCode in Kotlin
386. Lexicographical Numbers
Medium
Given an integer n, return all the numbers in the range [1, n] sorted in lexicographical order.
You must write an algorithm that runs in O(n) time and uses O(1) extra space.
Example 1:
Input: n = 13
Output: [1,10,11,12,13,2,3,4,5,6,7,8,9]
Example 2:
Input: n = 2
Output: [1,2]
Constraints:
1 <= n <= 5 * 104
Solution
class Solution {
fun lexicalOrder(n: Int): List<Int> {
val list = ArrayList<Int>()
fun recursion(x: Int) {
if (x > n) return
list.add(x)
for (i in 0..9) {
recursion(x * 10 + i)
}
}
for (i in 1..9) {
recursion(i)
}
return list
}
}