snailTraversal.js

/**
 * Given an array, rows and cols, transform the 1-D array into 2-D array organised in snail traversal order
 * Snail traversal starts at the top left cell with the first value of the given array,
 * then moves through the entire first column from top to bottom,
 * followed by moving to the next column on the right and traversing it from bottom to top.
 * This pattern continues, alternating the direction of traversal with each column until
 * the entire current array is covered.
 * @param {Array} array
 * @param {number} rows
 * @param {number} cols
 */
function snailTraversal(array, rows, cols) {
  if (
    !Array.isArray(array) ||
    typeof rows !== "number" ||
    typeof cols !== "number" ||
    rows <= 0 ||
    cols <= 0
  ) {
    throw new Error("Invalid input");
  }
  if (array.length !== rows * cols) {
    throw new Error("Invalid array length");
  }

  // Create the 2-D array
  const result = Array.from({ length: rows }, () => Array(cols).fill(0));

  for (let col = 0; col < cols; col++) {
    if (col % 2 === 0) {
      // Top to bottom
      for (let row = 0; row < rows; row++) {
        result[row][col] = array.shift();
      }
    } else {
      // Bottom to top
      for (let row = rows - 1; row >= 0; row--) {
        result[row][col] = array.shift();
      }
    }
  }

  return result;
}

module.exports = { snailTraversal };