Matrix

Instructions:

• Write a function that accepts an integer N and returns a NxN spiral matrix.

Examples:

matrix(2)
[[1, 2],
[4, 3]]
matrix(3)
[[1, 2, 3],
[8, 9, 4],
[7, 6, 5]]
matrix(4)
[[1, 2, 3, 4],
[12, 13, 14, 5],
[11, 16, 15, 6],
[10, 9, 8, 7]]

Repl.it:

• matrix

Code:

function matrix(n) {
  const results = [];
  for (let i = 0; i < n; i++) {
    results.push([]);
  }
  let counter = 1;
  let startColumn = 0;
  let endColumn = n - 1;
  let startRow = 0;
  let endRow = n - 1;
  while (startColumn <= endColumn && startRow <= endRow) {
    // Top row
    for (let i = startColumn; i <= endColumn; i++) {
      results[startRow][i] = counter;
      counter++;
    }
    startRow++;
    // Right column
    for (let i = startRow; i <= endRow; i++) {
      results[i][endColumn] = counter;
      counter++;
    }
    endColumn--;
    // Bottom row
    for (let i = endColumn; i >= startColumn; i--) {
      results[endRow][i] = counter;
      counter++;
    }
    endRow--;
    // start column
    for (let i = endRow; i >= startRow; i--) {
      results[i][startColumn] = counter;
      counter++;
    }
    startColumn++;
  }
  return results;
}