Star Rotation

Description

Consider a (2k+1) × (2k+1) square subarray of an integer integers matrix. Let’s call the union of the square’s two longest diagonals, middle column and middle row a star. Given the coordinates of the star’s center in the matrix and its width, rotate it 45 · t degrees clockwise preserving position of all matrix elements that do not belong to the star.

Example

For matrix = [[1, 0, 0, 2, 0, 0, 3], [0, 1, 0, 2, 0, 3, 0], [0, 0, 1, 2, 3, 0, 0], [8, 8, 8, 9, 4, 4, 4], [0, 0, 7, 6, 5, 0, 0], [0, 7, 0, 6, 0, 5, 0], [7, 0, 0, 6, 0, 0, 5]]

width = 7, center = [3, 3], and t = 1, the output should be

starRotation(matrix, width, center, t) = [[8, 0, 0, 1, 0, 0, 2], [0, 8, 0, 1, 0, 2, 0], [0, 0, 8, 1, 2, 0, 0], [7, 7, 7, 9, 3, 3, 3], [0, 0, 6, 5, 4, 0, 0], [0, 6, 0, 5, 0, 4, 0], [6, 0, 0, 5, 0, 0, 4]]

</code>
For

matrix = [[1, 0, 0, 2, 0, 0, 3], [0, 1, 0, 2, 0, 3, 0], [0, 0, 1, 2, 3, 0, 0], [8, 8, 8, 9, 4, 4, 4], [0, 0, 7, 6, 5, 0, 0]]

width = 3, center = [1, 5], and t = 81, the output should be

starRotation(matrix, width, center, t) = [[1, 0, 0, 2, 0, 0, 0], [0, 1, 0, 2, 3, 3, 3], [0, 0, 1, 2, 0, 0, 0], [8, 8, 8, 9, 4, 4, 4], [0, 0, 7, 6, 5, 0, 0]] Input/Output
[execution time limit] 4 seconds (js)
[input] array.array.integer matrix

A two-dimensional array of integers.

Guaranteed constraints:
3 ≤ matrix.length ≤ 15,
3 ≤ matrix[i].length ≤ 15,
matrix[i].length == matrix[j].length,
0 ≤ matrix[i][j] ≤ 99.
[input] integer width

An odd integer representing the star’s width. It equals the length of the sides of the bounding square for the star.

Guaranteed constraints:
3 ≤ width ≤ min(matrix.length, matrix[i].length).
[input] array.integer center

An array of two integers.

Guaranteed constraints:
center.length = 2,
(width - 1) / 2 ≤ center[0] < matrix.length - (width - 1) / 2,
(width - 1) / 2 ≤ center[1] < matrix[i].length - (width - 1) / 2.
[input] integer t

A non-negative integer denoting how many times the star should be rotated by 45 degrees.

Guaranteed constraints:
0 ≤ t ≤ 10⁹.
[output] array.array.integer
- An array with specified star rotated by ^{45 · t} degrees.

[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 starRotation(matrix, width, center, t) {
  var rotations = [
    (i) => [center[0] - i, center[1]],
    (i) => [center[0] - i, center[1] + i],
    (i) => [center[0], center[1] + i],
    (i) => [center[0] + i, center[1] + i],
    (i) => [center[0] + i, center[1]],
    (i) => [center[0] + i, center[1] - i],
    (i) => [center[0], center[1] - i],
    (i) => [center[0] - i, center[1] - i],
  ];
  var rotated = matrix.map((row) => row.slice());
  t = t % 8;
  for (var i = 1; i <= (width - 1) / 2; i++) {
    for (var j = 0; j < 8; j++) {
      rotated[rotations[(j + t) % 8](i)[0]][rotations[(j + t) % 8](i)[1]] =
        matrix[rotations[j](i)[0]][rotations[j](i)[1]];
    }
  }
  return rotated;
}

Codefights

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Star Rotation

Description

Solution