pratice

def merge_sort(arr):
    if len(arr)>1:
        mid=len(arr)//2
        left_half= arr[ :mid]
        right_half=arr[ mid:]
        
        merge_sort(left_half)
        merge_sort(right_half)
        merge(arr,left_half,right_half)

def merge(arr,left_half,right_half):
    i=j=k=0
    while i<len(left_half)and j<len(right_half):
        if left_half[i]<right_half[j]:
           arr[k]=left_half[i]
           i+=1
        else:
           arr[k]=right_half[j]
           j+=1
        k+=1
    
    while i<len(left_half):
      arr[k]=left_half[i]
      i+=1
      k+=1
    while j<len(right_half):
      arr[k]=right_half[j]
      j+=1
      k+=1
arr=[1,5,9,4,2,3]
merge_sort(arr)
print("sorted array",arr)