冒泡分类有什么问题?

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在课堂上,我们正在做排序算法,这是我在Python中的尝试:

mylist = [12, 5, 13, 8, 9, 65]

def bubble(badList):
    length = len(badList) - 1
    unsorted = True

    while unsorted:
        for element in range(0,length):
            unsorted = False
            if badList[element] > badList[element + 1]:
                hold = badList[element + 1]
                badList[element + 1] = badList[element]
                badList[element] = hold
                print badList
            else:
                unsorted = True

print bubble(mylist)

现在,这个(据我所知)排序是正确的,但是一旦它完成,它就会无限期地循环。

提问于
用户回答回答于

我将重命名变量unsortedsorted...一开始,您的列表还没有排序。当然,我们sortedFalse...

一旦我们开始while循环,我们假设列表已经排序。其思想是:一旦我们发现两个元素的顺序不对,我们就会设置sorted回到False...sorted将继续True只有当没有元素在错误的顺序.才结束

sorted = False  # We haven't started sorting yet

while not sorted:
    sorted = True  # Assume the list is now sorted
    for element in range(0, length):
        if badList[element] > badList[element + 1]:
            sorted = False  # We found two elements in the wrong order
            hold = badList[element + 1]
            badList[element + 1] = badList[element]
            badList[element] = hold
    # We went through the whole list. At this point, if there were no elements
    # in the wrong order, sorted is still True. Otherwise, it's false, and the
    # while loop executes again.

把这些都放在一起,你就会得到这个:

my_list = [12, 5, 13, 8, 9, 65]

def bubble(bad_list):
    length = len(bad_list) - 1
    sorted = False

    while not sorted:
        sorted = True
        for i in range(length):
            if bad_list[i] > bad_list[i+1]:
                sorted = False
                bad_list[i], bad_list[i+1] = bad_list[i+1], bad_list[i]

bubble(my_list)
print my_list
用户回答回答于

气泡排序在内部循环中,比较元素,您不必在每一轮中迭代整个列表...最重的已经排在最后了。互换变量是额外的,因此我们可以标记列表现在已经排序的变量,并避免继续进行不必要的计算。

def bubble(badList):
    length = len(badList)
    for i in range(0,length):
        swapped = False
        for element in range(0, length-i-1):
            if badList[element] > badList[element + 1]:
                hold = badList[element + 1]
                badList[element + 1] = badList[element]
                badList[element] = hold
                swapped = True
        if not swapped: break

    return badList

您的版本1,更正如下:

def bubble(badList):
    length = len(badList) - 1
    unsorted = True
    while unsorted:
        unsorted = False
        for element in range(0,length):
            #unsorted = False
            if badList[element] > badList[element + 1]:
                 hold = badList[element + 1]
                 badList[element + 1] = badList[element]
                 badList[element] = hold
                 unsorted = True
                 #print badList
             #else:
                 #unsorted = True

     return badList

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