Python 병합정렬 구현

1 개요

Python 병합정렬 구현
def merge(arr, left, middle, right):
    n1 = middle - left + 1
    n2 = right - middle
    L = [0] * (n1)
    R = [0] * (n2)
    for i in range(0 , n1):
        L[i] = arr[left + i]
    for j in range(0 , n2):
        R[j] = arr[middle + 1 + j]
    i = j = 0
    k = left
    while i < n1 and j < n2 :
        if L[i] <= R[j]:
            arr[k] = L[i]
            i += 1
        else:
            arr[k] = R[j]
            j += 1
        k += 1
    while i < n1:
        arr[k] = L[i]
        i += 1
        k += 1
    while j < n2:
        arr[k] = R[j]
        j += 1
        k += 1
def merge_sort(arr, left, right):
    if left < right:
        middle = int((left+(right-1))/2)
        merge_sort(arr, left, middle)
        merge_sort(arr, middle+1, right)
        merge(arr, left, middle, right)
arr = [3,4,2,1,7,5,8,9,0,6,100,10]
merge_sort(arr, 0, len(arr)-1)
print( arr )
# [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 100]
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