merge_sort implementation.

merge_sort.nim

import strutils
import math

#[
Module name: Implementation of MergeSort recursion.
Author: Benny E. 
Mail: elgazarbenny at gmail.com
]#


proc merge(left: seq[int], right: seq[int]): seq[int] =
    var 
        list: seq[int]
        i = 0
        j = 0
    list = @[]
    while list.len < (left.len + right.len):
        if left[i] < right[j]:
            list.add(left[i])
            i += 1
        else:
            list.add(right[j])
            j += 1
        if i == left.len or j == right.len:
            if i == left.len:
                list.add(right[j..right.len - 1])
            if j == right.len:
                list.add(left[i..left.len - 1])
            break
    return list


proc MergeSort*(s: seq[int]): seq[int] =
    if s.len < 2:
        return s
    var firstHalf = MergeSort(s[0..int(floor((s.len) / 2) - 1)])
    var secondHalf = MergeSort(s[int(floor((s.len) / 2))..(s.len - 1)])
    return merge(firstHalf, secondHalf)

discard MergeSort(@[7,48, 19, 9, 90])