| | | 1 | | // -------------------------------------------------------------------------------- |
| | | 2 | | // Copyright (C) 2025 Eugene Eremeev (also known as Yevhenii Yeriemeieiv). |
| | | 3 | | // All Rights Reserved. |
| | | 4 | | // -------------------------------------------------------------------------------- |
| | | 5 | | // This software is the confidential and proprietary information of Eugene Eremeev |
| | | 6 | | // (also known as Yevhenii Yeriemeieiv) ("Confidential Information"). You shall not |
| | | 7 | | // disclose such Confidential Information and shall use it only in accordance with |
| | | 8 | | // the terms of the license agreement you entered into with Eugene Eremeev (also |
| | | 9 | | // known as Yevhenii Yeriemeieiv). |
| | | 10 | | // -------------------------------------------------------------------------------- |
| | | 11 | | |
| | | 12 | | namespace LeetCode.Algorithms.KthSmallestInLexicographicalOrder; |
| | | 13 | | |
| | | 14 | | /// <inheritdoc /> |
| | | 15 | | public class KthSmallestInLexicographicalOrderPrefixTree : IKthSmallestInLexicographicalOrder |
| | | 16 | | { |
| | | 17 | | /// <summary> |
| | | 18 | | /// Time complexity - O(k * log n) |
| | | 19 | | /// Space complexity - O(1) |
| | | 20 | | /// </summary> |
| | | 21 | | /// <param name="n"></param> |
| | | 22 | | /// <param name="k"></param> |
| | | 23 | | /// <returns></returns> |
| | | 24 | | public int FindKthNumber(int n, int k) |
| | 8 | 25 | | { |
| | 8 | 26 | | var result = 1; |
| | | 27 | | |
| | 8 | 28 | | k--; |
| | | 29 | | |
| | 319 | 30 | | while (k > 0) |
| | 311 | 31 | | { |
| | 311 | 32 | | var nodesCount = GetNodesCount(result, n); |
| | | 33 | | |
| | 311 | 34 | | if (nodesCount <= k) |
| | 272 | 35 | | { |
| | 272 | 36 | | k -= nodesCount; |
| | 272 | 37 | | result++; |
| | 272 | 38 | | } |
| | | 39 | | else |
| | 39 | 40 | | { |
| | 39 | 41 | | result *= 10; |
| | 39 | 42 | | k--; |
| | 39 | 43 | | } |
| | 311 | 44 | | } |
| | | 45 | | |
| | 8 | 46 | | return result; |
| | 8 | 47 | | } |
| | | 48 | | |
| | | 49 | | private static int GetNodesCount(int prefix, int n) |
| | 311 | 50 | | { |
| | 311 | 51 | | var count = 0; |
| | 311 | 52 | | long current = prefix; |
| | 311 | 53 | | long next = prefix + 1; |
| | | 54 | | |
| | 1910 | 55 | | while (current <= n) |
| | 1599 | 56 | | { |
| | 1599 | 57 | | count += (int)(Math.Min(n + 1, next) - current); |
| | 1599 | 58 | | current *= 10; |
| | 1599 | 59 | | next *= 10; |
| | 1599 | 60 | | } |
| | | 61 | | |
| | 311 | 62 | | return count; |
| | 311 | 63 | | } |
| | | 64 | | } |