4kyu-snailSort.js

'use strict';

// Source: https://www.codewars.com/kata/521c2db8ddc89b9b7a0000c1/

// DESCRIPTION:

// Snail Sort

// Given an n x n array, return the array elements arranged from outermost 
// elements to the middle element, traveling clockwise.

// array = [[1,2,3],
//          [4,5,6],
//          [7,8,9]]
// snail(array) #=> [1,2,3,6,9,8,7,4,5]

// For better understanding, please follow the numbers of the next array 
// consecutively:

// array = [[1,2,3],
//          [8,9,4],
//          [7,6,5]]
// snail(array) #=> [1,2,3,4,5,6,7,8,9]

// NOTE: The idea is not sort the elements from the lowest value to the highest; 
// the idea is to traverse the 2-d array in a clockwise snailshell pattern.

// NOTE 2: The 0x0 (empty matrix) is represented as en empty array inside an 
// array [[]].


function snail(array) {
    let result = array[0].slice();
    let length = array.length;

    if (length === 1) return result;
    if (length === 2) return result.concat(array[1].slice().reverse());

    result = result.concat(array.slice(1, -1).map(a => a[length - 1]));
    result = result.concat(array[length - 1].slice().reverse());
    result = result.concat(array.slice(1, -1).reverse().map(a => a[0]));

    return result.concat(snail(array.slice(1, -1).map(a => a.slice(1, -1))));
}