Cinte's Leetcode Record
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36. Valid Sudoku

Posted on Edited on In Disqus:
Symbols count in article: 1.6k Reading time ≈ 1 mins.

36. Valid Sudoku

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class Solution {
public:
    bool isValidSudoku(vector<vector<char>>& board) {
        auto sz = board.size();
        int row[9][9]{0};
        int col[9][9]{0};
        int block[3][3][9]{0};
        for(size_t i = 0; i < 9; ++i)
        {
            for(size_t j = 0; j < 9; ++j)
            {
                auto num = board[i][j];
                if(num != '.')
                {
                    if(row[i][num - 49] == 1)
                        return false;
                    else
                        row[i][num - 49] += 1;
                    
                    if(col[num - 49][j] == 1)
                        return false;
                    else
                        col[num - 49][j] += 1;

                    if(block[i / 3][j / 3][num - 49] == 1)
                        return false;
                    else
                        block[i / 3][j / 3][num - 49] += 1;
                }
            }
        }
        return true;
    }
};

T : O(1) S : O(1)

more
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class Solution {
public:
    bool isValidSudoku(vector<vector<char>>& board) {
        auto sz = board.size();
        int row[9][9]{0};
        int col[9][9]{0};
        int block[3][3][9]{0};
        for(size_t i = 0; i < 9; ++i)
        {
            for(size_t j = 0; j < 9; ++j)
            {
                auto num = board[i][j];
                if(num != '.')
                {
                    if(row[i][num - 49] || col[num - 49][j] || block[i / 3][j / 3][num - 49])
                        return false;
                    else
                        row[i][num - 49] = col[num - 49][j] = block[i / 3][j / 3][num - 49] =  1;
                }
            }
        }
        return true;
    }
};
review
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class Solution {
public:
    bool isValidSudoku(vector<vector<char>>& board) {
        int row[9][9]{};
        int col[9][9]{};
        int square[9][9]{};
        for(int i = 0; i < 9; ++i)
        {
            for(int j = 0; j < 9; ++j)
            {
                if(board[i][j] == '.')
                    continue;
                int num = board[i][j] - '0' - 1;
                if(row[i][num] || col[j][num] || square[i / 3 + j / 3 * 3][num])
                    return false;
                row[i][num] = 1;
                col[j][num] = 1;
                square[i / 3 + j / 3 * 3][num] = 1;
            }
        }
        return true;
    }
};