| | | 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.ValidSudoku; |
| | | 13 | | |
| | | 14 | | /// <inheritdoc /> |
| | | 15 | | public class ValidSudokuBitmask : ValidSudokuBase |
| | | 16 | | { |
| | | 17 | | /// <summary> |
| | | 18 | | /// Time complexity - O(n^2) |
| | | 19 | | /// Space complexity - O(n) |
| | | 20 | | /// </summary> |
| | | 21 | | /// <param name="board"></param> |
| | | 22 | | /// <returns></returns> |
| | | 23 | | public override bool IsValidSudoku(char[][] board) |
| | 3 | 24 | | { |
| | 3 | 25 | | Span<int> rows = stackalloc int[N]; |
| | 3 | 26 | | Span<int> columns = stackalloc int[N]; |
| | 3 | 27 | | Span<int> boxes = stackalloc int[N]; |
| | | 28 | | |
| | 32 | 29 | | for (var rowIndex = 0; rowIndex < N; rowIndex++) |
| | 15 | 30 | | { |
| | 15 | 31 | | var row = board[rowIndex]; |
| | | 32 | | |
| | 278 | 33 | | for (var columnIndex = 0; columnIndex < N; columnIndex++) |
| | 126 | 34 | | { |
| | 126 | 35 | | var cell = row[columnIndex]; |
| | | 36 | | |
| | 126 | 37 | | if (cell == EmptyCell) |
| | 82 | 38 | | { |
| | 82 | 39 | | continue; |
| | | 40 | | } |
| | | 41 | | |
| | 44 | 42 | | var cellIndex = GetCellIndex(cell); |
| | | 43 | | |
| | 44 | 44 | | var bit = 1 << cellIndex; |
| | | 45 | | |
| | 44 | 46 | | var boxIndex = GetBoxIndex(rowIndex, columnIndex); |
| | | 47 | | |
| | 44 | 48 | | if (HasSeen(rows[rowIndex], bit) || |
| | 44 | 49 | | HasSeen(columns[columnIndex], bit) || |
| | 44 | 50 | | HasSeen(boxes[boxIndex], bit)) |
| | 2 | 51 | | { |
| | 2 | 52 | | return false; |
| | | 53 | | } |
| | | 54 | | |
| | 42 | 55 | | rows[rowIndex] |= bit; |
| | 42 | 56 | | columns[columnIndex] |= bit; |
| | 42 | 57 | | boxes[boxIndex] |= bit; |
| | 42 | 58 | | } |
| | 13 | 59 | | } |
| | | 60 | | |
| | 1 | 61 | | return true; |
| | 3 | 62 | | } |
| | | 63 | | |
| | | 64 | | private static bool HasSeen(int mask, int bit) |
| | 132 | 65 | | { |
| | 132 | 66 | | return (mask & bit) != 0; |
| | 132 | 67 | | } |
| | | 68 | | } |