改进版python实现的归并排序

Posted 2022-12-07 做人要厚道2013

def merge(a, begin, mid, end):

    left = a[begin:mid]
    right = a[mid:end]
    left.append(float("inf"))
    right.append(float("inf"))
    i = 0
    j = 0
    for k in range(begin, end):
        if left[i] < right[j]:
            a[k] = left[i]
            i = i + 1
        else:
            a[k] = right[j]
            j = j + 1


def merge_sort(a, begin, end):
    if begin == end - 1:
        return
    mid = (begin + end) >> 1
    merge_sort(a, begin, mid)
    merge_sort(a, mid, end)
    merge(a, begin, mid, end)


if __name__ == "__main__":
    a = [10, 2, 3, 6, 8, 1, 10, 100, 200, 6]  # , 3, 10, 4, 3, 10, 10, 4, 3, 10]
    print(a)
    merge_sort(a, 0, len(a))
    print(a)