| | | 1 | | // -------------------------------------------------------------------------------- |
| | | 2 | | // Copyright (C) 2026 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.MajorityFrequencyCharacters; |
| | | 13 | | |
| | | 14 | | /// <inheritdoc /> |
| | | 15 | | public sealed class MajorityFrequencyCharactersFrequencySpan : IMajorityFrequencyCharacters |
| | | 16 | | { |
| | | 17 | | private const byte AlphabetLength = 'z' - 'a' + 1; |
| | | 18 | | private const char FirstLetter = 'a'; |
| | | 19 | | |
| | | 20 | | /// <summary> |
| | | 21 | | /// Time complexity - O(n) |
| | | 22 | | /// Space complexity - O(1) |
| | | 23 | | /// </summary> |
| | | 24 | | /// <param name="s"></param> |
| | | 25 | | /// <returns></returns> |
| | | 26 | | public string MajorityFrequencyGroup(string s) |
| | 3 | 27 | | { |
| | 3 | 28 | | Span<int> letterFrequencies = stackalloc int[AlphabetLength]; |
| | | 29 | | |
| | 52 | 30 | | for (var i = 0; i < s.Length; i++) |
| | 23 | 31 | | { |
| | 23 | 32 | | var letter = s[i] - FirstLetter; |
| | | 33 | | |
| | 23 | 34 | | letterFrequencies[letter]++; |
| | 23 | 35 | | } |
| | | 36 | | |
| | 3 | 37 | | Span<int> groupSizes = stackalloc int[s.Length + 1]; |
| | | 38 | | |
| | 162 | 39 | | for (var i = 0; i < AlphabetLength; i++) |
| | 78 | 40 | | { |
| | 78 | 41 | | var frequency = letterFrequencies[i]; |
| | | 42 | | |
| | 78 | 43 | | if (frequency <= 0) |
| | 65 | 44 | | { |
| | 65 | 45 | | continue; |
| | | 46 | | } |
| | | 47 | | |
| | 13 | 48 | | groupSizes[frequency]++; |
| | 13 | 49 | | } |
| | | 50 | | |
| | 3 | 51 | | var maxFrequency = 0; |
| | 3 | 52 | | var maxSize = 0; |
| | | 53 | | |
| | 52 | 54 | | for (var frequency = 1; frequency < s.Length + 1; frequency++) |
| | 23 | 55 | | { |
| | 23 | 56 | | var size = groupSizes[frequency]; |
| | | 57 | | |
| | 23 | 58 | | if (size < maxSize) |
| | 17 | 59 | | { |
| | 17 | 60 | | continue; |
| | | 61 | | } |
| | | 62 | | |
| | 6 | 63 | | if (size == maxSize && frequency <= maxFrequency) |
| | 0 | 64 | | { |
| | 0 | 65 | | continue; |
| | | 66 | | } |
| | | 67 | | |
| | 6 | 68 | | maxFrequency = frequency; |
| | 6 | 69 | | maxSize = size; |
| | 6 | 70 | | } |
| | | 71 | | |
| | 3 | 72 | | Span<char> resultBuffer = stackalloc char[AlphabetLength]; |
| | | 73 | | |
| | 3 | 74 | | var resultLength = 0; |
| | | 75 | | |
| | 162 | 76 | | for (var i = 0; i < AlphabetLength; i++) |
| | 78 | 77 | | { |
| | 78 | 78 | | if (letterFrequencies[i] != maxFrequency) |
| | 70 | 79 | | { |
| | 70 | 80 | | continue; |
| | | 81 | | } |
| | | 82 | | |
| | 8 | 83 | | var character = (char)(FirstLetter + i); |
| | | 84 | | |
| | 8 | 85 | | resultBuffer[resultLength] = character; |
| | | 86 | | |
| | 8 | 87 | | resultLength++; |
| | 8 | 88 | | } |
| | | 89 | | |
| | 3 | 90 | | return new string(resultBuffer[..resultLength]); |
| | 3 | 91 | | } |
| | | 92 | | } |