Sudoku

Description

Sudoku is a number-placement puzzle. The objective is to fill a 9 × 9 grid with digits so that each column, each row, and each of the nine 3 × 3 sub-grids that compose the grid contains all of the digits from 1 to 9.

This algorithm should check if the given grid of numbers represents a correct solution to Sudoku.

Example

For

grid = [[1, 3, 2, 5, 4, 6, 9, 8, 7], [4, 6, 5, 8, 7, 9, 3, 2, 1], [7, 9, 8, 2, 1, 3, 6, 5, 4], [9, 2, 1, 4, 3, 5, 8, 7, 6], [3, 5, 4, 7, 6, 8, 2, 1, 9], [6, 8, 7, 1, 9, 2, 5, 4, 3], [5, 7, 6, 9, 8, 1, 4, 3, 2], [2, 4, 3, 6, 5, 7, 1, 9, 8], [8, 1, 9, 3, 2, 4, 7, 6, 5]]

the output should be sudoku(grid) = true;
For

grid = [[1, 3, 2, 5, 4, 6, 9, 2, 7], [4, 6, 5, 8, 7, 9, 3, 8, 1], [7, 9, 8, 2, 1, 3, 6, 5, 4], [9, 2, 1, 4, 3, 5, 8, 7, 6], [3, 5, 4, 7, 6, 8, 2, 1, 9], [6, 8, 7, 1, 9, 2, 5, 4, 3], [5, 7, 6, 9, 8, 1, 4, 3, 2], [2, 4, 3, 6, 5, 7, 1, 9, 8], [8, 1, 9, 3, 2, 4, 7, 6, 5]]

the output should be sudoku(grid) = false.

The output should be false: each of the nine 3 × 3 sub-grids should contain all of the digits from 1 to 9.
These examples are represented on the image below.

Input/Output

[execution time limit] 4 seconds (js)
[input] array.array.integer grid

A matrix representing 9 × 9 grid already filled with numbers from 1 to 9.

Guaranteed constraints:
grid.length = 9,
grid[i].length = 9,
1 ≤ grid[i][j] ≤ 9.
[output] boolean
- true if the given grid represents a correct solution to Sudoku, false otherwise.

[JavaScript (ES6)] Syntax Tips

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// Prints help message to the console
// Returns a string
function helloWorld(name) {
console.log("This prints to the console when you Run Tests");
return "Hello, " + name;
}

Solution

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function sudoku(grid) {
  var ret = true;
  ret = grid.every((row) => row.every((el, id, arr) => id === arr.indexOf(el)));
  ret =
    ret &&
    grid[0]
      .map((c, i) => grid.map((_, j) => grid[j][i]))
      .every((row) => row.every((el, id, arr) => id === arr.indexOf(el)));

  ret =
    ret &&
    grid
      .map((_, i) =>
        grid.map(
          (_, j) =>
            grid[Math.floor(i / 3) * 3 + Math.floor(j / 3)][
              (i % 3) * 3 + (j % 3)
            ]
        )
      )
      .every((row) => row.every((el, id, arr) => id === arr.indexOf(el)));
  return ret;
}

Codefights

A way to improve your programming skills.

Sudoku

Description

Solution