index.js

/*
 * @lc app=leetcode id=36 lang=javascript
 *
 * [36] Valid Sudoku
 *
 * https://leetcode.com/problems/valid-sudoku/description/
 *
 * algorithms
 * Medium (41.53%)
 * Total Accepted:    210.7K
 * Total Submissions: 507.1K
 * Testcase Example:  '[["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"]]'
 *
 * Determine if a 9x9 Sudoku board is valid. Only the filled cells need to be
 * validated according to the following rules:
 * 
 * 
 * Each row must contain the digits 1-9 without repetition.
 * Each column must contain the digits 1-9 without repetition.
 * Each of the 9 3x3 sub-boxes of the grid must contain the digits 1-9 without
 * repetition.
 * 
 * 
 * 
 * A partially filled sudoku which is valid.
 * 
 * The Sudoku board could be partially filled, where empty cells are filled
 * with the character '.'.
 * 
 * Example 1:
 * 
 * 
 * Input:
 * [
 * ⁠ ["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:
 * [
 * ["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.
 * 
 * 
 * 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.
 * The given board contain only digits 1-9 and the character '.'.
 * The given board size is always 9x9.
 * 
 * 
 */
/**
 * @param {character[][]} board
 * @return {boolean}
 */
var isValidSudoku = function(board) {
    const rowMap = Array.from({length:9}).map(() => ({}));
    const columnMap = Array.from({length:9}).map(() => ({}));
    const areaMap = [
        [{},{},{}],
        [{},{},{}],
        [{},{},{}],
    ];
    for (let i = 0; i < 9; i++) {
        for (let j = 0; j < 9; j++) {
            const curNum = board[i][j];
            if (curNum === '.') {
                continue;
            }
            if (rowMap[i][curNum]) {
                return false;
            }
            if (columnMap[j][curNum]) {
                return false;
            }
            const areaI = Math.floor(i / 3);
            const areaJ = Math.floor(j / 3);
            if (areaMap[areaI][areaJ][curNum]) {
                return false;
            }
            rowMap[i][curNum] = true;
            columnMap[j][curNum] = true;
            areaMap[areaI][areaJ][curNum] = true;
        }
    }
    return true;
};

const test1 = [
    ["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"]
];
console.log(isValidSudoku(test1));

module.exports = {
    id:'36',
    title:'Valid Sudoku',
    url:'https://leetcode.com/problems/valid-sudoku/description/',
    difficulty:'Medium',
}