LeetCode-in-Net/LeetCodeNet/G0001_0100/S0036_valid_sudoku/Solution.cs at main · jscrdev/LeetCode-in-Net · GitHub

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namespace LeetCodeNet.G0001_0100.S0036_valid_sudoku {

// #Medium #Top_Interview_Questions #Array #Hash_Table #Matrix #Data_Structure_I_Day_5_Array
// #Top_Interview_150_Matrix #2025_06_30_Time_1_ms_(98.25%)_Space_48.16_MB_(85.00%)

using System.Collections.Generic;

public class Solution {
    public bool IsValidSudoku(char[][] board) {
        bool[,] rows = new bool[9, 9];
        bool[,] cols = new bool[9, 9];
        bool[,] blocks = new bool[9, 9];
        for (int i = 0; i < board.Length; i++) {
            for (int j = i; j < board[i].Length; j++) {
                if (!isValidCase(board, i, j, rows, cols, blocks)) {
                    return false;
                }
                if (i != j && !isValidCase(board, j, i, rows, cols, blocks)) {
                    return false;
                }
            }
        }
        return true;
    }

    private bool isValidCase(char[][] board, int i, int j, bool[,] rows, bool[,] cols, bool[,] blocks) {
        if (board[i][j] == '.')
            return true;
        int num = board[i][j] - '1';
        int block = (i / 3) * 3 + (j / 3);
        if (rows[i, num] || cols[j, num] || blocks[block, num])
            return false;
        rows[i, num] = true;
        cols[j, num] = true;
        blocks[block, num] = true;
        return true;
    }
}
}