[LeetCode] 36. Valid Sudoku

https://leetcode.com/

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:

출처 : https://leetcode.com/problems/valid-sudoku/description/

nput: 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 '.'.

 

Code :

var isValidSudoku = function(board) {
    // 행 검사
    for (let row = 0; row < 9; row++) {
        const rowSet = new Set();
        for (let col = 0; col < 9; col++) {
            const cell = board[row][col];
            if (cell !== '.' && rowSet.has(cell)) {
                return false;
            }
            if (cell !== '.') {
                rowSet.add(cell);
            }
        }
    }

    // 열 검사
    for (let col = 0; col < 9; col++) {
        const colSet = new Set();
        for (let row = 0; row < 9; row++) {
            const cell = board[row][col];
            if (cell !== '.' && colSet.has(cell)) {
                return false;
            }
            if (cell !== '.') {
                colSet.add(cell);
            }
        }
    }

    // 3x3 서브 그리드 검사
    for (let block = 0; block < 9; block++) {
        const blockSet = new Set();
        const startRow = Math.floor(block / 3) * 3;
        const startCol = (block % 3) * 3;
        for (let i = 0; i < 3; i++) {
            for (let j = 0; j < 3; j++) {
                const cell = board[startRow + i][startCol + j];
                if (cell !== '.' && blockSet.has(cell)) {
                    return false;
                }
                if (cell !== '.') {
                    blockSet.add(cell);
                }
            }
        }
    }

    return true;
};

 

Solutions Code :

var isValidSudoku = function(board) {
    // 각 행, 열, 3x3 박스를 확인하기 위한 반복문
    for (let i = 0; i < board.length; i++) {
        let rowMap = {};
        let colMap = {};
        let boxMap = {};
        for (let j = 0; j < board[i].length; j++) {

            // 현재 위치의 3x3 박스를 찾는 과정
            let box = board[3 * Math.floor(i / 3) + Math.floor(j / 3)][3 * (i % 3) + (j % 3)];
            
            // 현재 위치의 값이 '.'이 아닌 경우 유효성을 확인
            if (board[i][j] != '.') {
                // 현재 행에 값이 중복되는 경우 유효하지 않음
                if (rowMap[board[i][j]]) return false;
                rowMap[board[i][j]] = 1;
            }
            if (board[j][i] != '.') {
                // 현재 열에 값이 중복되는 경우 유효하지 않음
                if (colMap[board[j][i]]) return false;
                colMap[board[j][i]] = 1;
            }
            if (box != '.') {
                // 현재 3x3 박스에 값이 중복되는 경우 유효하지 않음
                if (boxMap[box]) return false;
                boxMap[box] = 1;
            }
        }
    }
    return true;
};

 

 

출처 : https://leetcode.com/problemset/all/

Problems - LeetCode