Today I have done leetcode's November LeetCoding Challenge with cpp.

November LeetCoding Challenge 23

Description

Valid Sudoku

Determine if a 9 x 9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:

1. Each row must contain the digits 1-9 without repetition.
2. Each column must contain the digits 1-9 without repetition.
3. Each of the nine 3 x 3 sub-boxes of the grid must contain the digits 1-9 without repetition.

Note:

• A Sudoku board (partially filled) could be valid but is not necessarily solvable.
• Only the filled cells need to be validated according to the mentioned rules.

Example 1:

Input: board = 
[["5","3",".",".","7",".",".",".","."]
,["6",".",".","1","9","5",".",".","."]
,[".","9","8",".",".",".",".","6","."]
,["8",".",".",".","6",".",".",".","3"]
,["4",".",".","8",".","3",".",".","1"]
,["7",".",".",".","2",".",".",".","6"]
,[".","6",".",".",".",".","2","8","."]
,[".",".",".","4","1","9",".",".","5"]
,[".",".",".",".","8",".",".","7","9"]]
Output: true

Example 2:

Input: board = 
[["8","3",".",".","7",".",".",".","."]
,["6",".",".","1","9","5",".",".","."]
,[".","9","8",".",".",".",".","6","."]
,["8",".",".",".","6",".",".",".","3"]
,["4",".",".","8",".","3",".",".","1"]
,["7",".",".",".","2",".",".",".","6"]
,[".","6",".",".",".",".","2","8","."]
,[".",".",".","4","1","9",".",".","5"]
,[".",".",".",".","8",".",".","7","9"]]
Output: false
Explanation: Same as Example 1, except with the 5 in the top left corner being modified to 8. Since there are two 8's in the top left 3x3 sub-box, it is invalid.

Constraints:

• board.length == 9
• board[i].length == 9
• board[i][j] is a digit 1-9 or '.'.

Solution

auto speedup = [](){
  cin.tie(nullptr);
  cout.tie(nullptr);
  ios::sync_with_stdio(false);
  return 0;
}();
class Solution {
  bool visRow[9][9] = {};
  bool visCol[9][9] = {};
  bool visBox[9][9] = {};
public:
  bool isValidSudoku(vector<vector<char>>& board) {
    for(int row = 0; row < 9; ++row) {
      for(int col = 0; col < 9; ++col) {
        int box = row / 3 * 3 + col / 3;
        int digit = board[row][col] == '.' ? -1 : board[row][col] - '1';
        if(digit == -1) continue;
        if(visRow[row][digit] || visCol[col][digit] || visBox[box][digit]) return false;
        visRow[row][digit] = true;
        visCol[col][digit] = true;
        visBox[box][digit] = true;
      }
    }
    return true;
  }
};

// Accepted
// 507/507 cases passed (12 ms)
// Your runtime beats 98.39 % of cpp submissions
// Your memory usage beats 72.54 % of cpp submissions (18 MB)