problem-65.js

/**
 * Company: Amazon.
 *
 * Given a N by M matrix of numbers, print out the matrix in a clockwise spiral.
 * For example, given the following matrix:
 * [[1,  2,  3,  4,  5],
 * [6,  7,  8,  9,  10],
 * [11, 12, 13, 14, 15],
 * [16, 17, 18, 19, 20]]
 * You should print out the following:
 * 1
 * 2
 * 3
 * 4
 * 5
 * 10
 * 15
 * 20
 * 19
 * 18
 * 17
 * 16
 * 11
 * 6
 * 7
 * 8
 * 9
 * 14
 * 13
 * 12
 */
var spiralOrder = function(matrix) {
  if (matrix.length === 0) return [];

  const result = [];
  let rowBegin = 0;
  let rowEnd = matrix.length - 1;
  let colBegin = 0;
  let colEnd = matrix[0].length - 1;

  while (rowBegin <= rowEnd && colBegin <= colEnd) {
    for (let j = colBegin; j <= colEnd; j++) {
      result.push(matrix[rowBegin][j]);
    }
    rowBegin++;

    for (let i = rowBegin; i <= rowEnd; i++) {
      result.push(matrix[i][colEnd]);
    }
    colEnd--;

    if (rowBegin <= rowEnd) {
      for (let j = colEnd; j >= colBegin; j--) {
        result.push(matrix[rowEnd][j]);
      }
    }
    rowEnd--;

    if (colBegin <= colEnd) {
      for (let i = rowEnd; i >= rowBegin; i--) {
        result.push(matrix[i][colBegin]);
      }
    }
    colBegin++;
  }

  return result;
};