day5冒泡排序

　　冒泡排序：是一种基础的算法，实现数据的排序，排序的原则是前一个与后一个进行比较，如果前面的值大则交换，否则不交换，多次循环每次把最大的数据循环至后面就能够完成所需。

上面的图是冒泡排序的原理，每次循环把最大的值遍历到最后面，而且循环的过程中，每次循环的次数减1。

下面来看一个实例，我们将一个列表data = [10,4,33,21,54,3,8,11,5,22,2,1,17,13,6],我们将列表进行排序。代码如下：

首先取出列表的顺序和下表enumerate(

data = [10,4,33,21,54,3,8,11,5,22,2,1,17,13,6]

　　for index,i in enumerate(data[0:-1]):
　　if i > data[index+1]:
　　　　data[index+1],data[index] = i,data[index+1]
　　print(data)
    运行如下：

　　[4, 10, 21, 33, 3, 54, 8, 5, 11, 2, 1, 2, 13, 6, 13]

　　可以看出是调换了位置，但是是有错误的。13出现了两次，22消失了，这是由于在循环过程中，我们改动了列表的下标，改动下标之后就出现了错误，有些值被替换了。因为不能这样做，或者下面这样也是不行的。

　　data = [10,4,33,21,54,3,8,11,5,22,2,1,17,13,6]

　　for index,i in enumerate(data[0:-1]):
　　　　if i > data[index+1]:
　　　　#data[index+1],data[index] = i,data[index+1]
　　　　#存储一个临时变量用来存储信息
　　　　　　tmp = data[index+1]
　　　　　　data[index+1] = i
　　　　　　data[index] = tmp

　　　　print(data)

上面代码中tem的作用是存储一个data[index+1]因为我们知道，要把data[index]和data[index+1]进行交换，如果单纯的交换，有一个会被替换，因为要把被替换的值存在一个新的变量中，这样就避免了这种错误。

　　data = [10,4,33,21,54,3,8,11,5,22,2,1,17,13,6]

　　for j in range(len(data)):
　　　　for i in range(len(data)-1):
　　　　　　if data[i] > data[i+1]:
　　　　　　tem = data[i+1]
　　　　　　data[i+1] = data[i]
　　　　　　data[i] = tem
　　print(data)

运行代码结果如下：

　　[1, 2, 3, 4, 5, 6, 8, 10, 11, 13, 17, 21, 22, 33, 54]

　　上面代码中，我们的思路是循环列表中的每个元素，前一个和后一个进行比较，如果前一个大于后一个就进行替换，否则不动，这样每次把最后一个最大值移到列表的末尾，就能实现功能，列表有多少长度，我们就循环多少次，因此我们在外面加入了for循环，让下面的列表排序能够进行多次比较。但是上面的代码可以有一个改进的地方，我们知道，每次循环都会把一个最大值放到列表的末尾，因此循环的次数可以每次递减1次，下面我们对代码进行改进：

　　data = [10,4,33,21,54,3,8,11,5,22,2,1,17,13,6]

　　for j in range(1,len(data)):
　　　　for i in range(len(data)-j):
　　　　　　if data[i] > data[i+1]:
　　　　　　　　tem = data[i+1]
　　　　　　　　data[i+1] = data[i]
　　　　　　　　data[i] = tem
　　print(data)

运行结果如下：

　　[1, 2, 3, 4, 5, 6, 8, 10, 11, 13, 17, 21, 22, 33, 54]

　　结果是一样的，但是我们这里避免了很多不必要的循环，我们看一下两个代码各自需要循环多少次，为此我们可以定义一个n在里面，每次循环的时候加1。

data = [10,4,33,21,54,3,8,11,5,22,2,1,17,13,6]
　　n = 0
　　for j in range(len(data)):
　　#for j in range(1,len(data)):
　　　　for i in range(len(data)-1):
　　　　#for i in range(len(data) - j):
　　　　n = n + 1
　　　　if data[i] > data[i+1]:
　　　　　　tem = data[i+1]
　　　　　　data[i+1] = data[i]
　　　　　　data[i] = tem
　　print(n)
　　print(data)

经过上面两种方法的测试，没有改进的方法运行了210次，改进之后的方法值运行了105次，可见很多时候改进一点点就能节省很多时间。

下面来看看代码每次运行的结果：

　　[4, 10, 33, 21, 54, 3, 8, 11, 5, 22, 2, 1, 17, 13, 6]
　　[4, 10, 21, 33, 54, 3, 8, 11, 5, 22, 2, 1, 17, 13, 6]
　　[4, 10, 21, 33, 3, 54, 8, 11, 5, 22, 2, 1, 17, 13, 6]
　　[4, 10, 21, 33, 3, 8, 54, 11, 5, 22, 2, 1, 17, 13, 6]
　　[4, 10, 21, 33, 3, 8, 11, 54, 5, 22, 2, 1, 17, 13, 6]
　　[4, 10, 21, 33, 3, 8, 11, 5, 54, 22, 2, 1, 17, 13, 6]
　　[4, 10, 21, 33, 3, 8, 11, 5, 22, 54, 2, 1, 17, 13, 6]
　　[4, 10, 21, 33, 3, 8, 11, 5, 22, 2, 54, 1, 17, 13, 6]
　　[4, 10, 21, 33, 3, 8, 11, 5, 22, 2, 1, 54, 17, 13, 6]
　　[4, 10, 21, 33, 3, 8, 11, 5, 22, 2, 1, 17, 54, 13, 6]
　　[4, 10, 21, 33, 3, 8, 11, 5, 22, 2, 1, 17, 13, 54, 6]
　　[4, 10, 21, 33, 3, 8, 11, 5, 22, 2, 1, 17, 13, 6, 54]
　　[4, 10, 21, 3, 33, 8, 11, 5, 22, 2, 1, 17, 13, 6, 54]
　　[4, 10, 21, 3, 8, 33, 11, 5, 22, 2, 1, 17, 13, 6, 54]
　　[4, 10, 21, 3, 8, 11, 33, 5, 22, 2, 1, 17, 13, 6, 54]
　　[4, 10, 21, 3, 8, 11, 5, 33, 22, 2, 1, 17, 13, 6, 54]
　　[4, 10, 21, 3, 8, 11, 5, 22, 33, 2, 1, 17, 13, 6, 54]
　　[4, 10, 21, 3, 8, 11, 5, 22, 2, 33, 1, 17, 13, 6, 54]
　　[4, 10, 21, 3, 8, 11, 5, 22, 2, 1, 33, 17, 13, 6, 54]
　　[4, 10, 21, 3, 8, 11, 5, 22, 2, 1, 17, 33, 13, 6, 54]
　　[4, 10, 21, 3, 8, 11, 5, 22, 2, 1, 17, 13, 33, 6, 54]
　　[4, 10, 21, 3, 8, 11, 5, 22, 2, 1, 17, 13, 6, 33, 54]
　　[4, 10, 3, 21, 8, 11, 5, 22, 2, 1, 17, 13, 6, 33, 54]
　　[4, 10, 3, 8, 21, 11, 5, 22, 2, 1, 17, 13, 6, 33, 54]
　　[4, 10, 3, 8, 11, 21, 5, 22, 2, 1, 17, 13, 6, 33, 54]
　　[4, 10, 3, 8, 11, 5, 21, 22, 2, 1, 17, 13, 6, 33, 54]
　　[4, 10, 3, 8, 11, 5, 21, 2, 22, 1, 17, 13, 6, 33, 54]
　　[4, 10, 3, 8, 11, 5, 21, 2, 1, 22, 17, 13, 6, 33, 54]
　　[4, 10, 3, 8, 11, 5, 21, 2, 1, 17, 22, 13, 6, 33, 54]
　　[4, 10, 3, 8, 11, 5, 21, 2, 1, 17, 13, 22, 6, 33, 54]
　　[4, 10, 3, 8, 11, 5, 21, 2, 1, 17, 13, 6, 22, 33, 54]
　　[4, 3, 10, 8, 11, 5, 21, 2, 1, 17, 13, 6, 22, 33, 54]
　　[4, 3, 8, 10, 11, 5, 21, 2, 1, 17, 13, 6, 22, 33, 54]
　　[4, 3, 8, 10, 5, 11, 21, 2, 1, 17, 13, 6, 22, 33, 54]
　　[4, 3, 8, 10, 5, 11, 2, 21, 1, 17, 13, 6, 22, 33, 54]
　　[4, 3, 8, 10, 5, 11, 2, 1, 21, 17, 13, 6, 22, 33, 54]
　　[4, 3, 8, 10, 5, 11, 2, 1, 17, 21, 13, 6, 22, 33, 54]
　　[4, 3, 8, 10, 5, 11, 2, 1, 17, 13, 21, 6, 22, 33, 54]
　　[4, 3, 8, 10, 5, 11, 2, 1, 17, 13, 6, 21, 22, 33, 54]
　　[3, 4, 8, 10, 5, 11, 2, 1, 17, 13, 6, 21, 22, 33, 54]
　　[3, 4, 8, 5, 10, 11, 2, 1, 17, 13, 6, 21, 22, 33, 54]
　　[3, 4, 8, 5, 10, 2, 11, 1, 17, 13, 6, 21, 22, 33, 54]
　　[3, 4, 8, 5, 10, 2, 1, 11, 17, 13, 6, 21, 22, 33, 54]
　　[3, 4, 8, 5, 10, 2, 1, 11, 13, 17, 6, 21, 22, 33, 54]
　　[3, 4, 8, 5, 10, 2, 1, 11, 13, 6, 17, 21, 22, 33, 54]
　　[3, 4, 5, 8, 10, 2, 1, 11, 13, 6, 17, 21, 22, 33, 54]
　　[3, 4, 5, 8, 2, 10, 1, 11, 13, 6, 17, 21, 22, 33, 54]
　　[3, 4, 5, 8, 2, 1, 10, 11, 13, 6, 17, 21, 22, 33, 54]
　　[3, 4, 5, 8, 2, 1, 10, 11, 6, 13, 17, 21, 22, 33, 54]
　　[3, 4, 5, 2, 8, 1, 10, 11, 6, 13, 17, 21, 22, 33, 54]
　　[3, 4, 5, 2, 1, 8, 10, 11, 6, 13, 17, 21, 22, 33, 54]
　　[3, 4, 5, 2, 1, 8, 10, 6, 11, 13, 17, 21, 22, 33, 54]
　　[3, 4, 2, 5, 1, 8, 10, 6, 11, 13, 17, 21, 22, 33, 54]
　　[3, 4, 2, 1, 5, 8, 10, 6, 11, 13, 17, 21, 22, 33, 54]
　　[3, 4, 2, 1, 5, 8, 6, 10, 11, 13, 17, 21, 22, 33, 54]
　　[3, 2, 4, 1, 5, 8, 6, 10, 11, 13, 17, 21, 22, 33, 54]
　　[3, 2, 1, 4, 5, 8, 6, 10, 11, 13, 17, 21, 22, 33, 54]
　　[3, 2, 1, 4, 5, 6, 8, 10, 11, 13, 17, 21, 22, 33, 54]
　　[2, 3, 1, 4, 5, 6, 8, 10, 11, 13, 17, 21, 22, 33, 54]
　　[2, 1, 3, 4, 5, 6, 8, 10, 11, 13, 17, 21, 22, 33, 54]
　　[1, 2, 3, 4, 5, 6, 8, 10, 11, 13, 17, 21, 22, 33, 54]

上面是分布每次运行的情况，下面是没一大步运行的情况：

　　[4, 10, 21, 33, 3, 8, 11, 5, 22, 2, 1, 17, 13, 6, 54]
　　[4, 10, 21, 3, 8, 11, 5, 22, 2, 1, 17, 13, 6, 33, 54]
　　[4, 10, 3, 8, 11, 5, 21, 2, 1, 17, 13, 6, 22, 33, 54]
　　[4, 3, 8, 10, 5, 11, 2, 1, 17, 13, 6, 21, 22, 33, 54]
　　[3, 4, 8, 5, 10, 2, 1, 11, 13, 6, 17, 21, 22, 33, 54]
　　[3, 4, 5, 8, 2, 1, 10, 11, 6, 13, 17, 21, 22, 33, 54]
　　[3, 4, 5, 2, 1, 8, 10, 6, 11, 13, 17, 21, 22, 33, 54]
　　[3, 4, 2, 1, 5, 8, 6, 10, 11, 13, 17, 21, 22, 33, 54]
　　[3, 2, 1, 4, 5, 6, 8, 10, 11, 13, 17, 21, 22, 33, 54]
　　[2, 1, 3, 4, 5, 6, 8, 10, 11, 13, 17, 21, 22, 33, 54]
　　[1, 2, 3, 4, 5, 6, 8, 10, 11, 13, 17, 21, 22, 33, 54]
　　[1, 2, 3, 4, 5, 6, 8, 10, 11, 13, 17, 21, 22, 33, 54]
　　[1, 2, 3, 4, 5, 6, 8, 10, 11, 13, 17, 21, 22, 33, 54]
　　[1, 2, 3, 4, 5, 6, 8, 10, 11, 13, 17, 21, 22, 33, 54]

当然还有一种简单的方法能够实现列表的排序，而且只需要循环列表长度的次数即可：

　　data = [10,4,33,21,54,3,8,11,5,22,2,1,17,13,6]
　　numbers = []
　　#查找列表中最小值的位置
　　for i in range(len(data)):
　　　　num = data.pop(data.index(min(data)))
　　　　numbers.append(num)
　　print(numbers)

方法的原理是，我们知道，目的是实现列表中元素的排序，那么我们每次找到列表中的最小值并且把这个最小值使用pop方法弹出来，那么列表的长度每次减1，我们每次都只找最小值，使用index()查找值的索引，使用另外一个列表去接收。就能够实现，运行结果如下：

　　[1, 2, 3, 4, 5, 6, 8, 10, 11, 13, 17, 21, 22, 33, 54]