alternateSort()

/**
 * @author: K. Lae Kettavong
 * 
 * @date: 3/04/19
 * 
 * @description: Coding challenge, function to generate alternate array from given array and determine if new array is sorted
 * 
 *  You are given an array of integers a. A new array b is generated by rearranging the elements of a in the following way:
 *
 *  b[0] is equal to a[0];
 *  b[1] is equal to the last element of a;
 *  b[2] is equal to a[1];
 *  b[3] is equal to the second-last element of a;
 *  and so on.
 *  Your task is to determine whether the new array b is sorted in strictly ascending order or not.
 *
 *  Example
 *
 *  For a = [1, 3, 5, 6, 4, 2], the output should be alternatingSort(a) = true.
 *
 *  The new array b will look like [1, 2, 3, 4, 5, 6], which is in strictly ascending order, so the answer is true.
 *
 *  For a = [1, 4, 5, 6, 3], the output should be alternatingSort(a) = false.
 *
 *  The new array b will look like [1, 3, 4, 6, 5], which is not in strictly ascending order, so the answer is false.
 *
 */

const alternateSort = (inputArray) => {
    if(!Array.isArray(inputArray) || inputArray.length === 0) return false
    let revArray = [...inputArray].reverse()
    let newArray = []
    let len = Math.ceil(inputArray.length / 2)
    let ndx = 0
    
    while (ndx < len) {
        newArray.push(inputArray[ndx]) 
        if( newArray.length < inputArray.length) {
            newArray.push(revArray[ndx])
        }
        ndx++
    }

    const isSorted = isArraySorted(newArray)
    console.log(newArray, isSorted)
    return isSorted
}

const isArraySorted = (inputArray) => {
    let ndx = 0
    while (ndx < inputArray.length - 1) {
      if(inputArray[ndx] > inputArray[++ndx]) return false
    }
    return true
}

// O(2n) -> O(n) -> linear time
console.log(alternateSort('hello'))
console.log(alternateSort(1,2,3))
console.log(alternateSort([]))
alternateSort([1, 3, 5, 6, 4, 2])
alternateSort([1, 4, 5, 6, 3])
alternateSort([1])
alternateSort([1, 2])
alternateSort([1, 3, 2])
alternateSort([-89, -47, -38, 39, 82, 87, 40, -9, -41, -68])
alternateSort([-92, -17, 71, 76, 54, -35])
alternateSort([-52, 2, 31, 56, 47, 29, -35])
alternateSort([-97, -51, -8, 25, 44, 70, 98, 77, 68, 31, -5, -36, -80])
alternateSort([-86, -49, -26, -22, 22, 32, 44, 67, 38, 25, 13, -25, -42, -71])
alternateSort([-92, -23, 0, 45, 89, 96, 99, 95, 89, 41, -17, -48])
alternateSort([-37, -31, -8, 88, -10, -33])
alternateSort([-87, -52, 83, 96, 98, 94, 68, -71])
alternateSort([-92, 9, 41, 99, 29, -78])
alternateSort([-91, -84, -67, -44, 9, 70, 88, 37, -11, -67, -72, -87])
alternateSort([-44, -73, -24, 22, 91, 84, 2, -40, -56])
alternateSort([-79, -48, -42, 4, 9, 55, 70, 84, 62, 40, 7, -28, -46, -74])
alternateSort([-27, -81, -7, 21, 33, 52, 23, -6, -10, -71])
alternateSort( [-99, -29, -7, 17, 28, 71, 98, 86, 42, 22, 0, -29, -86])
alternateSort([-86, 93, 4, 27, 49, 74, 74, -70, 60, 41, 14, -44, -80])
alternateSort([42, -80, -72, -25, 18, -94, 99, 49, 37, 10, -45, -76, -87])