我有下面的代码Python代码的理解
def compare_and_swap(x, a, b):
if x[a] > x[b]:
x[a], x[b] = x[b], x[a]
def oddeven_merge(x, lo, hi, r):
step = r * 2
if step < hi - lo:
oddeven_merge(x, lo, hi, step)
oddeven_merge(x, lo + r, hi, step)
for i in range(lo + r, hi - r, step):
compare_and_swap(x, i, i + r)
else:
compare_and_swap(x, lo, lo + r)
def oddeven_merge_sort_range(x, lo, hi):
""" sort the part of x with indices between lo and hi.
Note: endpoints (lo and hi) are included.
"""
if (hi - lo) >= 1:
# if there is more than one element, split the input
# down the middle and first sort the first and second
# half, followed by merging them.
mid = lo + ((hi - lo)/2)
oddeven_merge_sort_range(x, lo, mid)
oddeven_merge_sort_range(x, mid + 1, hi)
oddeven_merge(x, lo, hi, 1)
def oddeven_merge_sort(x):
oddeven_merge_sort_range(x, 0, len(x)-1)
>>> data = [4, 3, 5, 6, 1, 7, 8]
>>> oddeven_merge_sort(data)
>>> data
[1, 2, 3, 4, 5, 6, 7, 8]
一切都清楚了我,但仅此线不能很好地理解
for i in range(lo + r, hi - r, step):
我如何使用它的伪代码?或阅读其他语言例如C++?
你有什么是非常危险的,可以永远循环。我不相信它相当于python的范围。 – Mat
@Mat:对。它可能会永远循环,但我无法想象一种在C语言中同时适用于积极和消极“步骤”的方式。我正在更新我的答案,只为正面案例工作。 – MAK
+1负面的一步好点。 –