Rotate-Transform the Two-Dimensional Matrix in js-CodePudding

I have to create a function to rotate a two-dimensional matrix of N * N integer elements num times, where if num is positive, the rotation is clockwise, and if not, counterclockwise.

Examples

rotateTransform([
   [2, 4],
   [0, 0]
], 1) /*➞ [
   [0, 2],
   [0, 4]
]*/

rotateTransform([
   [2, 4],
   [0, 0]
], -1) /*➞ [
   [4, 0],
   [2, 0]
]*/

NOTE: I couldn't even try...

CodePudding user response：

the same problem on edabit, and this was the top solution, IDK why you reposting it here...

function rotateTransform(arr, num) {
  if (num > 0)
    return rotateTransform(arr.map((_, i) => arr.map(x => x[i]).reverse()), num - 1);
  else if (num < 0)
    return rotateTransform(arr.map((_, i) => arr.map(x => x[i])).reverse(), num   1);
  else
    return arr;
}

console.log(rotateTransform([
  [2, 4],
  [0, 0]
], 1))

console.log(rotateTransform([
  [2, 4],
  [0, 0]
], -1))

CodePudding user response：

For every possible num you enter there are only 3 other orientations and you can get there with at most 2 transforms:

function rotateTransform(arr, num) {
  // turn 90deg clockwise
  if (num & 1) arr = arr.reverse().map((_, i) => arr.map(row => row[i]));
  // turn 180deg
  if (num & 2) arr.reverse().forEach(row => row.reverse());

  return arr;
}

for (let num = -10; num < 10;   num) {
  console.log("num", num);
  console.log(rotateTransform([
    [2, 4],
    [0, 0]
  ], num).join("\n"))
}

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