使用python实现归并排序

Posted 2022-12-10 做人要厚道2013

def merge(left, right):
    """归并两个数组
    :param left: 第一个数组
    :param right:  第二个数组
    :return: 归并后的有序的的数组
    """
    print("left", left)
    print("right", right)

    i, j = 0, 0
    n1, n2 = len(left), len(right)
    r = []
    while i < n1 and j < n2:
        while i < n1:
            if j == n2:
                break
            if left[i] <= right[j]:
                r.append(left[i])
            else:
                break
            i += 1
        while j < n2:
            if i == n1:
                break
            if right[j] <= left[i]:
                r.append(right[j])
            else:
                break
            j += 1
    r.extend(left[i:])
    r.extend(right[j:])
    return r


def merge_sort(a):
    """
    使用递归来完成归并
    :param a: 要排序的数组
    :return:  返回值为排好序的数组
    """
    if len(a) == 1:
        return a

    mid = len(a) >> 1

    left = merge_sort(a[:mid])  # 给左边排序
    right = merge_sort(a[mid:])  # 给右边排序
    return merge(left, right)


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)
    b = merge_sort(a)
    print(b)