valid-sudoku.js

// 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.
//
//


/*
[".87654321",
 "2........",
 "3........",
 "4........",
 "5........",
 "6........",
 "7........",
 "8........",
 "9........"]
 */


/**
 * @param {character[][]} board
 * @return {boolean}
 */
var isValidSudoku = function(board) {
    var r = new Array(9),
        c = new Array(9),
        b = new Array(9);
    var i, j;
    for (i = 0;i < 9;++i) {
        r[i] = new Array(9);
        c[i] = new Array(9);
        b[i] = new Array(9);
    }

    for (i = 0;i < 9;++i) {
        for (j = 0;j < 9;++j) {
            if (board[i][j] === '.') {
                continue;
            }
            var temp = +board[i][j] - 1;
            if (r[i][temp] || c[temp][j] || 
                    b[~~(j/3)+~~(i/3)*3][temp]) {
                return false;
            }
            r[i][temp] = c[temp][j] = b[~~(j/3)+~~(i/3)*3][temp] = true;
        }
    }
    return true;
};