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Assignment2 Solution

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Submission instructions

  1. You should submit your homework on GitHubopen in new window.
  2. For this assignment you should turn in 4 separate .py files named according to the following pattern:
    hw1_q1.py, hw1_q2.py, etc.
  3. Each Python file you submit should contain a header comment block as follows:
"""
Author: [Your name here]
Assignment / Part: HW1 - Q1 (etc.)
Date due: 2023-02-09, 11:59pm
I pledge that I have completed this assignment without
collaborating with anyone else, in conformance with the
Bornforthis 1v1 School of Computer Science and Procedures on
Academic Misconduct.
"""

No late submissions will be accepted.

REMINDER: Do not use any Python structures that we have not learned in class.

注意

下面英文有可能表述没那么到位,如果感觉英文表达有优化的地方,欢迎在评论区留言指出来哈。不胜感激~

Question 01: Find the Missing Number

Acquire user input, where the user inputs a specific list. This list consists of consecutive numerical elements. However, one number is missing. Please write a program to find the missing number without using any built-in functions.

Sample Test 1:

Enter the list of numbers: 1, 2, 3, 4, 6, 7, 8
The missing number is 5.

Sample Test 2:

Enter the list of numbers: 1,2, 4, 5,6, 7,8
The missing number is 3.

Note: Here's a useful hint for the map function and a tip for solving the problem.

Map Function Usage:

  • The map() function in Python applies a given function to each item of an iterable (like a list) and returns a map object (which is an iterator).
string_numbers = ['1', '2', '3', '99', '101', '131']
int_numbers = list(map(int, string_numbers))
print(int_numbers)


# ---output---
[1, 2, 3, 99, 101, 131]

Solution 01:

input_numbers = input('Enter the list of numbers:').replace(' ', '').split(",")
numbers = list(map(int, input_numbers))
max_number = len(numbers) + 1
expected_sum = max_number * (max_number + 1) // 2
missing_number = expected_sum - sum(numbers)
print(f'The missing number is {missing_number}.')
ZH

获取用户输入,用户输入特定列表,这个列表是的元素数字且是连续的。但是其中会缺少一个数字,请编写一个程序,在不使用内置函数的情况下找出缺少的数字。

Sample Test 1:

Enter the list of numbers: 1, 2, 3, 4, 6, 7, 8
The missing number is 5.

Sample Test 2:

Enter the list of numbers: 1, 2, 4, 5, 6, 7, 8
The missing number is 3.

Question 02: List Rotation

Prompt the user to input a specific series of numbers separated by commas. The last number represents the position to which the list will be left-rotated. All numbers before the last one are elements of the list. Do not use any built-in functions.

Sample Test:

Please enter a series of numbers separated by commas: 1, 2, 3, 4, 5, 2
List [1, 2, 3, 4, 5] After left-hand rotation [3, 4, 5, 1, 2]

Note: Here's a useful hint for the map function and a tip for solving the problem.

Map Function Usage:

  • The map() function in Python applies a given function to each item of an iterable (like a list) and returns a map object (which is an iterator).
string_numbers = ['1', '2', '3', '99', '101', '131']
int_numbers = list(map(int, string_numbers))
print(int_numbers)


# ---output---
[1, 2, 3, 99, 101, 131]
ZH

获取用户输入,用户输入特定的一系列数字以逗号分隔,最后一个数字代表将列表左旋到指定位置。最后一个数字之前的都是列表的元素,不使用任何内置函数。

Solution 02:

# 用户输入的数字序列
user_input = input('Please enter a series of numbers separated by commas:').replace(' ', '').split(',')
# 将字符串转换为整数列表
numbers_list = list(map(int, user_input))
# 从列表中提取旋转次数和剩余的数字
# *rotating_elements, rotation_count = numbers
rotating_elements, rotation_count = numbers_list[:-1], numbers_list[-1]
# 执行左旋转操作
rotated_list = rotating_elements[rotation_count:] + rotating_elements[:rotation_count]
# 输出结果
print(f"List {rotating_elements} after {rotation_count} left rotations: {rotated_list}")

Question 03: Shallow Copy Verification

Demonstrate shallow copying of a list and show how it differs from a deep copy.

Solution 03:

# Demonstrating shallow copying and deep copying in Python

# Original list
original_list = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

# Shallow copy of the list
shallow_copy = original_list.copy()

# Deep copy of the list
import copy
deep_copy = copy.deepcopy(original_list)

# Altering the original list to show the difference
original_list[0][0] = 'X'

# Displaying the original list, shallow copy, and deep copy to illustrate the differences
print("Original:", original_list)
print("Shallow Copy:", shallow_copy)
print("Deep Copy:", deep_copy)

To demonstrate the difference between shallow and deep copying, let's analyze the results after modifying the original list:

  1. Original List: After modification, the original list becomes [['X', 2, 3], [4, 5, 6], [7, 8, 9]]. We changed the first element of the first sub-list from 1 to 'X'.

  2. Shallow Copy: The shallow copy also reflects this change, showing [['X', 2, 3], [4, 5, 6], [7, 8, 9]]. In a shallow copy, the nested lists are not copied, so when the nested lists in the original list are modified, the changes appear in the shallow copy as well.

  3. Deep Copy: The deep copy remains unchanged, showing [[1, 2, 3], [4, 5, 6], [7, 8, 9]]. This is because a deep copy creates a new independent copy of the entire data structure, including all nested objects. Thus, changes in the original list do not affect the deep copy.

This comparison illustrates that a shallow copy only copies the outer list, while a deep copy copies both the outer list and all nested lists.

Question 04: List to String Conversion

Obtain a user-input list and a specific delimiter, and concatenate the items in the user-input list into a string using the specified delimiter.

Sample Test 1:

Please enter a list of elements, separated by commas: apple, banana, orange
Please enter the delimiter you wish to use: ;
apple; banana; orange

Sample Test 2:

Please enter a list of elements, separated by commas: dog, cat, mouse
Please enter the delimiter you wish to use:  - 
dog -  cat -  mouse

Sample Test 3:

Please enter a list of elements, separated by commas: Monday, Tuesday, Wednesday, Thursday, Friday
Please enter the delimiter you wish to use: , 
Monday,  Tuesday,  Wednesday,  Thursday,  Friday

Sample Test 4:

Please enter a list of elements, separated by commas: 1, 2, 3, 4, 5
Please enter the delimiter you wish to use:  * 
1 *  2 *  3 *  4 *  5
zh

获取用户输入列表、和特定间隔符号,使用户输入的列表以特定间隔组成字符串。

# Prompt the user to enter a list of elements, assuming they are separated by commas
elements_input = input("Please enter a list of elements, separated by commas: ")

# Prompt for the delimiter the user wants to use
delimiter = input("Please enter the delimiter you wish to use: ")

# Split the input string into a list based on commas
elements_list = elements_input.split(',')

# Join the elements of the list into a string, using the specified delimiter
custom_string = delimiter.join(elements_list)

# Print the resulting string
print(custom_string)

Question 05: List Symmetry Check

Check if a list is symmetric (the same forwards and backwards).

Sample Test 1:

Enter a list of items separated by commas: 1, 2, 3, 2, 3
Is the entered list symmetric: False

Sample Test 2:

Enter a list of items separated by commas: 1,2, 3, 2, 1
Is the entered list symmetric: True

Solution 05:

# Get user input
user_input = input("Enter a list of items separated by commas: ").replace(' ', '')

# Convert the input string to a list
# The elements will remain as string type
lst = user_input.split(',')

# Check if the list is symmetric
is_symmetric = lst == lst[::-1]

print(f"Is the entered list symmetric: {is_symmetric}")

Question 06: List Element Swapping

Write a program to swap two elements in a list.

Receive user input, where the user inputs a series of numbers. The last two numbers are the indices to be swapped.

Sample Test 1:

Enter list elements followed by two positions to swap, all separated by space: 1, 2, 3, 4, 5, 1, 3
List after swapping elements: ['1', '4', '3', '2', '5']

Sample Test 2:

Enter list elements followed by two positions to swap, all separated by space: a,b, c, d, e , 0, 3
List after swapping elements: ['d', 'b', 'c', 'a', 'e']
zh

获取用户输入,用户输入一系列数字,倒数第一和第二是待交换的下标。

# 用户在一行内输入列表和两个交换位置,用空格分隔
input_data = input("Enter list elements followed by two positions to swap, all separated by space: ").replace(' ', '')

# 解析输入数据
parts = input_data.split(',')
lst = parts[:-2]
pos1 = int(parts[-2])
pos2 = int(parts[-1])

# 执行交换
lst[pos1], lst[pos2] = lst[pos2], lst[pos1]

# 打印结果
print("List after swapping elements:", lst)

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