Merge-Sort
Merge sort is an example of a divide-and-conquer type sorting-algorithm.The input of merge sort is an array of some elements, which are need to be arranged typically from least to the greatest.
Steps to follow in Merge Sort
- Merge sort divides the array in to two sub arrays and later divides each array in to another two arrays and so on until a bunch of single element arrays are left. For instance, in the following example the array [4,7,5,9,1,3,8,2] divides in to single array elements such as [4], [7], [5], [9], [1], [3], [8], [2].
- It starts comparing arrays in such a manner that two arrays are compared and concatenated. In the following example, it compares two arrays at a time that is [4], [7] are compared and concatenated then [5], [9] are compared and concatenated and so on such that arrays [4,7], [5,9], [1,3], [2,8] are formed.
- It follows the same way that is two-two arrays are compared and concatenated to form two arrays. In the following example [4,7] and [5,9] are compared and concatenated to get an array as [4,5,7,9] and same is the case with other two arrays to form an array as [1,2,3,8].
- Same rule applicable here that is the remaining two arrays compares and concatenates to get a final array as [1,2,3,4,5,7,8,9].
Example
<html> <body> <script> function mSort (array) { if (array.length === 1) { return array // return once we hit an array with a single item } const middle = Math.floor(array.length / 2) // get the middle item of the array rounded down const left = array.slice(0, middle) // items on the left side const right = array.slice(middle) // items on the right side document.write(middle); return merge( mSort(left), mSort(right) ) } // compare the arrays item by item and return the concatenated result function merge (left, right) { let result = [] let leftIndex = 0 let rightIndex = 0 while (leftIndex < left.length && rightIndex < right.length) { if (left[leftIndex] < right[rightIndex]) { result.push(left[leftIndex]) leftIndex++ document.write("</br>"); } else { result.push(right[rightIndex]) rightIndex++ } } return result.concat(left.slice(leftIndex)).concat(right.slice(rightIndex)) } const list = [4,7,5,9,1,3,8,2] document.write(mSort(list)); </script> </body> </html>
Output
1,2,3,4,5,7,8,9