Practice 2: Strings, Lists and Functions

Guide (Please read!!!)

There are 3 levels of difficulty of practice problems which will help guide you on how you do the assignment.

1. Concept (★☆☆) will help you recheck yourself whether you understood the content.
2. Apply (★★☆) will step up some difficulty where you have to apply several concepts.
3. Technique (★★★) is more challenging.

The problems will state inputs and outputs of the program. Inputs and outputs can be more than one, one each, see examples for more details.

Problems

(★☆☆) 1. String Reverse

Write a program that print the reversed version of the string.

Input:

1. a string from user

Output:

1. a reversed string

Examples

Input:  hello world!
-----
Output: !dlrow olleh'

(★☆☆) 2. String Conversion

Write a program that does the following:

Hint: See len(...) function in Python.

Input:

1. a string s from user
2. an integer a from user

Output:

1. the length (how many characters) of the string s
2. first a characters of s
3. last a characters of s

Examples

Input:  phoomkung
        3
-----
Output: 9
        pho
        ung

(★☆☆) 3. Find substring

A substring is a string contained within a string. An empty string is a substring of every string. Write the program that does the following:

Input:

1. a string s from user
2. a string t, which will be the substring, from user

Output:

1. the index of first occurrences of substring t in string s. If s does not contain t, the program must not raise an exception (no error when not found).

Examples

Input:  This is so exiting!
        is
-----
Output: 2

Because 'This is so exiting!'
           ~~

(★☆☆) 4. Find substring (from the right)

From 3. and some useful string methods from searching Google, Write the program that does the following:

Input:

1. a string s from user
2. a string t, which will be the substring, from user

Output:

1. the index of last occurrences of substring t in string s. If s does not contain t, the program must not raise an exception (no error when not found).

Examples

Input:  This is so exiting!
        is
-----
Output: 5

Because 'This is so exiting!'
              ~~

(★☆☆) 5. Sort the list (1)

Write a program that sort the list e in ascending order. You will have to do only some parts of the program. Copy the template code below and read I/O instructions.

Template (copy and fill code)

# These are inputs
e = [int(input()) for i in range(int(input()))]

# Write your code here to sort the list
# and print the sorted list.
# There are many ways to do this.

Input:

1. a number n which determines how many elements are there in the list
2. Next n lines: an integer which will be in the list

Output:

1. A sorted list

Examples

Input:  4
        7
        6
        9
        2
-----
Output: [2, 6, 7, 9]

(★☆☆) 6. Sort the list (2)

Write a program that sort the list e in descending order. You will have to do only some parts of the program. Copy the template code below and read I/O instructions.

Do not use [::-1]

Template (copy and fill code)

# These are inputs
e = [int(input()) for i in range(int(input()))]

# Write your code here to sort the list
# and print the sorted list.
# There are many ways to do this.

Input:

1. an integer n which determines how many elements are there in the list
2. Next n lines: an integer which will be in the list

Output:

1. A sorted list

Examples

Input:  4
        7
        6
        9
        2
-----
Output: [9, 7, 6, 2]

(★☆☆) 7. Pop it off!

Write a program that remove en element of the list at index i.

Template (copy and fill code)

# These are inputs
e = [4, 9, 7, 4, 4, 4, 6, 2]

# Write your code here

Input:

1. an integer i

Output:

1. A list e with element at index i removed.
2. element that has been removed

Examples

Input:  3
-----
Output: [4, 9, 7, 4, 4, 6, 2]
        4
        
Because 4 is at index 3 in the original list.

(★☆☆) 8. Split it…

Write a program that split an input s into a list. The string is split by space.

Input:

1. a string s

Output:

1. A list from s

Examples

Input:  hello test test 1 2 3
-----
Output: ['hello', 'test', 'test', '1', '2', '3']

(★★☆) 9. and join it!

Write a program that split an input s into a list. The string is split by space. Then, join them by space but in reversed order.

Remarks Reversed order means reversed order of words, not every character.

Input:

1. a string s

Output:

1. a reversed order of s

Examples

Input:  hello test test 1 2 3
-----
Output: 3 2 1 test test hello

(★★☆) 10. Sort the tuples

Write a program that sort the list of k-tuples.

Template (copy and fill code)

# These are inputs
n = int(input())
e = [tuple([int(x) for x in input().split()]) for i in range(n)]

# Your code begin
x = e
# Use x as output list
# Your code end

for elem in x:
    print(*elem, sep=' ')

Input:

1. an integer n which determines how many tuples are there in the list

Output:

1. A sorted (descending order) list of tuples x

Examples

Input:  4 5 6
        7 8 9
        1 2 2
        
# e becomes [(4, 5, 6), (7, 8, 9), (1, 2, 2)]

-----
Output: 7 8 9
        4 5 6
        1 2 2

(★☆☆) 11. 4-mean

Write a function that returns geometric mean of 4 numbers by:

G.M. = (a * b * c * d) ^ 0.25

Template (copy and fill code)

# Your code begin
def f(w, x, y, z):
    ...
# Your code end

print(f(1, 3, 4, 5))

Input:

1. None

Output:

1. G.M. of 4 numbers

Examples

Input:  -
-----
Output: 2.7831576837137404

(★★☆) 12. Starry night: *args

Variadic argument function is a function that can take indefinite number of arguments. The function is not limited to taking only specified number of arguments in the function definition (def). In Python, we use *args in the argument to take any number of argument, then when we use it in the function as a list named args.

Write a function that takes any number of numbers as arguments and output a sum of all numbers.

Hint: See sum(...) function in Python.

Example of usages

# This function will print everything separated by comma ', '.
def print_all(*args):
    print(', '.join(args))
    
print_all('x', 'hello', 'sth')
# Output will be: x, hello, sth

Template (copy and fill code)

# Your code begin
def f(*args):
    ...
# Your code end

print(f(9, 8, 7, 6, 100))

Input:

1. None

Output:

1. Sum of all numbers

Examples

Input:  -
-----
Output: 130

(★★☆) 13. Keyword arguments

In some builtin functions in Python, they support “keyword arguments.” They are usually used for options. See examples

Example of usages

# Try these:
# print(...) in Python
print('hello', 'world', 'everyone!', sep='_', end='k')
print('hello', 'world', 'everyone!', sep=None, end='\nThe End La.')

This could be useful in the future when you work on I/O.

(★★☆) 14. Max and min

Write a program that calculate the max and min of all numbers user input.

Hint 1: See max(...) and min(...) functions in Python.

Input:

1. An integer n specifying how many numbers will the user input.
2. Next n lines: floating point numbers.

Output:

1. Maximum of all numbers
2. Minimum of all numbers

Examples

Input:  4
        1
        -10
        9.999
        7.6
-----
Output: 9.999
        -10

(★★☆) 15. Difference between alphabets!

The alphabets and any characters in computer have their encodings (numbers representing them). For example, difference between 'A' and 'F' is 5. Also, difference between 'a' and 'A' is 32.

(See ASCII Code or UTF-8 encoding for more information.)

Hint: See ord(...) function in Python and think of what to do with it.

Input:

1. First character c1
2. Second character c2

Output:

1. Difference between c1 and c2 (c2' - c1')

Examples

Input:  A
        G
-----
Output: 6

Other problems

Please see Assignment 2…