day5冒泡排序
冒泡排序:是一種基礎(chǔ)的算法,實(shí)現(xiàn)數(shù)據(jù)的排序,排序的原則是前一個(gè)與后一個(gè)進(jìn)行比較,如果前面的值大則交換,否則不交換,多次循環(huán)每次把最大的數(shù)據(jù)循環(huán)至后面就能夠完成所需。
???
??? 上面的圖是冒泡排序的原理,每次循環(huán)把最大的值遍歷到最后面,而且循環(huán)的過程中,每次循環(huán)的次數(shù)減1。
??? 下面來看一個(gè)實(shí)例,我們將一個(gè)列表data = [10,4,33,21,54,3,8,11,5,22,2,1,17,13,6],我們將列表進(jìn)行排序。代碼如下:
??? 首先取出列表的順序和下表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)
??? 運(yùn)行如下:
[4, 10, 21, 33, 3, 54, 8, 5, 11, 2, 1, 2, 13, 6, 13]
可以看出是調(diào)換了位置,但是是有錯(cuò)誤的。13出現(xiàn)了兩次,22消失了,這是由于在循環(huán)過程中,我們改動(dòng)了列表的下標(biāo),改動(dòng)下標(biāo)之后就出現(xiàn)了錯(cuò)誤,有些值被替換了。因?yàn)椴荒苓@樣做,或者下面這樣也是不行的。
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]
#存儲(chǔ)一個(gè)臨時(shí)變量用來存儲(chǔ)信息
tmp = data[index+1]
data[index+1] = i
data[index] = tmp
print(data)
??? 上面代碼中tem的作用是存儲(chǔ)一個(gè)data[index+1]因?yàn)槲覀冎?#xff0c;要把data[index]和data[index+1]進(jìn)行交換,如果單純的交換,有一個(gè)會(huì)被替換,因?yàn)橐驯惶鎿Q的值存在一個(gè)新的變量中,這樣就避免了這種錯(cuò)誤。
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)
??? 運(yùn)行代碼結(jié)果如下:
[1, 2, 3, 4, 5, 6, 8, 10, 11, 13, 17, 21, 22, 33, 54]
上面代碼中,我們的思路是循環(huán)列表中的每個(gè)元素,前一個(gè)和后一個(gè)進(jìn)行比較,如果前一個(gè)大于后一個(gè)就進(jìn)行替換,否則不動(dòng),這樣每次把最后一個(gè)最大值移到列表的末尾,就能實(shí)現(xiàn)功能,列表有多少長度,我們就循環(huán)多少次,因此我們在外面加入了for循環(huán),讓下面的列表排序能夠進(jìn)行多次比較。但是上面的代碼可以有一個(gè)改進(jìn)的地方,我們知道,每次循環(huán)都會(huì)把一個(gè)最大值放到列表的末尾,因此循環(huán)的次數(shù)可以每次遞減1次,下面我們對(duì)代碼進(jìn)行改進(jìn):
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)
??? 運(yùn)行結(jié)果如下:
[1, 2, 3, 4, 5, 6, 8, 10, 11, 13, 17, 21, 22, 33, 54]
結(jié)果是一樣的,但是我們這里避免了很多不必要的循環(huán),我們看一下兩個(gè)代碼各自需要循環(huán)多少次,為此我們可以定義一個(gè)n在里面,每次循環(huán)的時(shí)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)
??? 經(jīng)過上面兩種方法的測試,沒有改進(jìn)的方法運(yùn)行了210次,改進(jìn)之后的方法值運(yùn)行了105次,可見很多時(shí)候改進(jìn)一點(diǎn)點(diǎn)就能節(jié)省很多時(shí)間。
??? 下面來看看代碼每次運(yùn)行的結(jié)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]
??? 上面是分布每次運(yùn)行的情況,下面是沒一大步運(yùn)行的情況:
[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]
??? 當(dāng)然還有一種簡單的方法能夠?qū)崿F(xiàn)列表的排序,而且只需要循環(huán)列表長度的次數(shù)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,我們知道,目的是實(shí)現(xiàn)列表中元素的排序,那么我們每次找到列表中的最小值并且把這個(gè)最小值使用pop方法彈出來,那么列表的長度每次減1,我們每次都只找最小值,使用index()查找值的索引,使用另外一個(gè)列表去接收。就能夠?qū)崿F(xiàn),運(yùn)行結(jié)果如下:
[1, 2, 3, 4, 5, 6, 8, 10, 11, 13, 17, 21, 22, 33, 54]
轉(zhuǎn)載于:https://www.cnblogs.com/gengcx/p/6798950.html
總結(jié)
- 上一篇: bash中 21 的解释
- 下一篇: 从零到一:用Phaser.js写意地开发