Concurrent Merge Sort (Go)

solution_1.go

/************
Concurrent Merge Sort
using goroutine and channel only
**************/
package main
import "fmt"
         

func Merge(left, right [] int) [] int{
  merged := make([] int, 0, len(left) + len(right))
  for len(left) > 0 || len(right) > 0{
    if len(left) == 0 {
      return append(merged,right...)
    }else if len(right) == 0 {
      return append(merged,left...)
    }else if left[0] < right[0] {
      merged = append(merged, left[0])
      left = left[1:]
    }else{
      merged = append(merged, right [0])
      right = right[1:]
    }
  }
  return merged
}

func MergeSort(data [] int, channel chan [] int) {
  
  defer close(channel) // clean up

  if len(data) <= 1 { 
    channel <- data
    return
  }
  
  mid := len(data)/2
  left_channel := make(chan [] int)
  right_channel := make(chan [] int)
  go MergeSort(data[:mid],left_channel)
  go MergeSort(data[mid:],right_channel)

  left  := <-left_channel  // block unitl recieve
  right := <-right_channel // block unitl recieve

  channel <- Merge(left,right)
  

}

func main(){
  data := [] int{9,4,3,6,1,2,10,5,7,8}

   merge_channel := make(chan [] int) // on each sort call create a new channel

  go MergeSort(data,merge_channel)
  
  fmt.Printf("%v\n%v\n", data, <-merge_channel)
}

solution_2.go

package main
import "fmt"

func Merge(left, right [] int) [] int{
  merged := make([] int, 0, len(left) + len(right))
  for len(left) > 0 || len(right) > 0{
    if len(left) == 0 {
      return append(merged,right...)
    }else if len(right) == 0 {
      return append(merged,left...)
    }else if left[0] < right[0] {
      merged = append(merged, left[0])
      left = left[1:]
    }else{
      merged = append(merged, right [0])
      right = right[1:]
    }
  }
  return merged
}

func MergeSort(data [] int) [] int {
  if len(data) <= 1 {
    return data
  }
  done := make(chan bool)
  mid := len(data)/2
  var left [] int
  
  go func(){
    left = MergeSort(data[:mid])
    done <- true
  }()
  right := MergeSort(data[mid:])
  <-done
  return Merge(left,right)

}

func main(){
  data := [] int{9,4,3,6,1,2,10,5,7,8}
  fmt.Printf("%v\n%v\n", data, MergeSort(data))

}