package main

import "fmt"

func merge(left []int,right []int) []int{
    //Merge two lists in ascending order.
    lst:=make([]int,0)
    for len(left) > 0 && len(right) > 0{
        if left[0] < right[0]{
            lst = append(lst,left[0])
            left = left[1:]
        }else{
            lst = append(lst,right[0])
            right = right[1:]
        }
    }
    if len(left) > 0{
        lst = append(lst,left...)
    }
    if  len(right) > 0{
        lst = append(lst,right...)
    }

    return lst
}

func mergesort(lst []int) []int{
    //Sort the list by merging O(n * log n).
    length:=len(lst)
    if length >= 2{
        mid := length/2
        lst = merge(mergesort(lst[:mid]),mergesort(lst[mid:]))
    }
    return lst
}

func main(){

    lst := []int{2,123,443,223,3,5,6,432,1}
    lst = mergesort(lst)
    fmt.Println(lst)
}