苍穹外卖

1

Write a program to solve a classic ancient Chinese puzzle:
We count 35 heads and 94 legs among the chickens and rabbits in a
farm. How many rabbits and how many chickens do we have?

Use for loop to iterate all possible solutions.

分析：鸡的数量从0开始数，使用for循环，直到鸡兔腿数和等于94，输出并跳出循环

heads = 35
legs = 94
chickens = 0
for chickens in range(0,heads):
    if heads*4-chickens*2 == legs:
        print("chickens:",chickens)
        print("rabbits:",heads-chickens)
        break

运行截图

2

Please write a program which prints all permutations of [1,2,3]

Use itertools.permutations() to get permutations of list.

分析: itertools.permutations()函数返回的是可迭代元素的全排列
如果直接输出则返回它所在的地址，需要使用for循环遍历所有排列

import itertools
for i in itertools.permutations([1,2,3]):
    print(i , end=" ")

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3

Please write a program which accepts a string from console and print
the characters that have even indexes.

Use list[::2] to iterate a list by step 2.

分析：输入字符串并以步长为2输出字符，可以使用input()读入，并使用list[::2]进行输出

list = input("请输入：")
print(list[::2])

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4

Please write a program which accepts a string from console and print
it in reverse order.

Use list[::-1] to iterate a list in a reverse order.

分析：list[::-1]中的-1表示逆向以步长为1输出字符

list = input("请输入：")
print(list[::-1])

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5

Please write a program which count and print the numbers of each
character in a string input by console.

Use dict to store key/value pairs.
Use dict.get() method to lookup a key with default value.

分析：使用字典dict进行统计，
dict.get(key, default=None)
返回指定键的值，如果键不在字典中返回 default 设置的默认值

st = input("请输入：")
d = { }
for i in st:
    d[i]=d.get(i,0)+1
for i in d:
    print(i,",",d[i])

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6

Define a class Person and its two child classes: Male and Female. All
classes have a method “getGender” which can print “Male” for Male
class and “Female” for Female class.

Use Subclass(Parentclass) to define a child class.

分析：主要考察了类的继承，以及父类方法的覆写

class Person:
    def getGender (self):
        return "unknown"

class Male(Person):
    def getGender(self):
        return  "Male"
class Female(Person):
    def getGender(self):
        return "Female"
one =Male()
two =Female()
print(one.getGender())
print(two.getGender())

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7

With a given list [12,24,35,24,88,120,155,88,120,155], write a program
to print this list after removing all duplicate values with original order
reserved.

Use set() to store a number of values without duplicate.

分析：主要考察集合set
set() 创建空集合
set.add() 添加新元素

list = [12,24,35,24,88,120,155,88,120,155]
s = set()
for i in list:
    s.add(i)
for i in s:
    print(i , end=" ")

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8

By using list comprehension, please write a program to print the list
after removing the value 24 in [12,24,35,24,88,120,155].

Use list’s remove method to delete a value

分析：
s1 &=s2 相当于 s1= s1&s2 即取s1和s2的交集并赋给s1

s1 = {1,3,6,78,35,55}
s2 = {12,24,35,24,88,120,155}
s1 &= s2
li =list(s1)
print(li)

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9

By using list comprehension, please write a program to print the list
after removing the value 24 in [12,24,35,24,88,120,155].

Use list’s remove method to delete a value.
分析：使用del删除第二个元素即24

li = [12,24,35,24,88,120,155]
del li[1] #删除24
print(li)

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10

By using list comprehension, please write a program to print the list
after removing the 0th,4th,5th numbers in [12,24,35,70,88,120,155].

Use list comprehension to delete a bunch of element from a
list.
Use enumerate() to get (index, value) tuple.

分析：主要考察推导式和enumerate() 函数
enumerate() 函数用于将一个可遍历的数据对象(如列表、元组或字符串)组合为一个索引序列，同时列出数据和数据下标，一般用在 for 循环当中。

li = [12,24,35,70,88,120,155]
li = [x for (i,x) in enumerate(li) if i not in (0,4,5)]
print(li)

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