Why sometimes you have to push() before you sort()

This algorithm is actually called Where do I belong?.

Challenge:

For example:

Some helpful links:

• Array.sort()

You know your code has passed when:

What I was given to work with as a start:

My pseudo code for the challenge:

arr.sort(): sorts the elements of an array in place and returns the array. The sort is not necessarily stable. The default sort order is according to Unicode code points.

arr.sort() parameters:

compareFunction: Optional. Specifies a function that defines the sort order. If omitted, the array is sorted according to each character’s Unicode code point value, according to the string conversion of each element.

compareFunction description (if compareFunction is not supplied): elements are sorted by converting them to strings and comparing strings in Unicode code point order. For example, “banana” comes before “cherry”. In a numeric sort, 9 comes before 80, but because numbers are converted to strings, “80” comes before “9” in Unicode order.

compareFunction description (if compareFunction is supplied): array elements are sorted according to the return value of the compare function. If a and b are two elements being compared, then:

• if compareFunction(a, b) is < 0, sort a to a lower index than b, i.e., a comes first.
• if compareFunction(a, b) === 0, leave a & b unchanged with respect to each other, but sorted with respect to all different elements. Note: the ECMAscript standard does not guarantee this behaviour, and thus not all browsers (e.g. Mozilla versions dating back to at least 2003) respect this.
• if compareFunction(a,b) > 0, sort be to a lower index than a.
• compareFunction(a, b) must always return the same value when given a specific pair of elements a and b as its two arguments. If inconsistent results are returned then the sort order is undefined.

Articulation of my solution:

1. I knew that I had to push the second (provided) argument (num) into the first argument (arr) before I could do anything else. This is represented by arr.push(num);
2. Then I knew that I had to sort this “new” array. This is represented by arr.sort(compareFunction), which is in turn represented by arr.sort(function(a, b) { return a-b }.
3. Lastly, I had to “return the index of the pushed number after the array has been sorted”. This is represented by return arr.indexOf(num). To learn more about how .indexOf() works, please visit my earlier post Why Array.prototype.slice.call() is helpful when working with both arrays and objects.

My solution to the challenge:

Solution in ES6:

This was first published here on May 5, 2016 @ 14:55. It was part of freecodecamp.org’s Basic JavaScript Algorithm Scripting for the Front End Development certification.

Related articles

• Count minimum steps to get the given desired array
• Insert, Remove, and Replace elements with Array.splice()