String problem solving :: Python programming (2024)

Class Objectives

• Practice problem solving in string data types.
• Learn how to interpret real world problem into computer problem
• More flexible usage of loops and conditionals
• Dive deeper to string data structure
• Process large and multi-dimensional string data in practice

Problems

• Loop through strings
• Character sorting
• Type check
• String reverse
• Add suffix to string

Loop through strings

Requirements

Given a string consists of repeated characters. Write a function to process the string to return number of repeated characters in a dictionary.

• Not allowed to use string.count(character) function
• Your are encouraged to solve the problem with algorithms

Input:

string = "The more that you read, the more things you will know, the more that you learn, the more places you willl go."

Output:

{'T': 1, 'h': 7, 'e': 11, ' ': 21, 'm': 4, 'o': 10, 'r': 6, 't': 8, 'a': 5, 'y': 4, 'u': 4, 'd': 1, ',': 3, 'i': 3, 'n': 3, 'g': 2, 's': 2, 'w': 3, 'l': 7, 'k': 1, 'p': 1, 'c': 1, '.': 1}

Problem solving pattern

• Step 1: Define a function with a parameter
• Step 2: Define a dictionary
• Step 3: Loop through the string
• Step 4: Get keys of dictionary. keys = dict.keys() returns a list of keys
• Step 5: Check if each character in the string exists in the keys.
• Step 6: If it exists in the keys, increment it’s value by 1, if not assign a value 1.

Character sorting

Requirements

Given a string of random characters. Write a function to sort them in English alphabatical order.

• Noe allowed to use Python sort functions
• Solve the problem with algorithms

Problem solving pattern

Input:

string = 'dsajlvwjeoijvdskavljwioenvjskdlahj'

Output:

aaadddeehiijjjjjjkklllnoosssvvvvww

Hint

• You may consider Python chr() and ord()

Type check

Requirements

Given string of random letters, digits and symbols. Write a function to return them in different lists.

• You are encouraged to use regex

Input:

import re string = 'fjsdlkajlv463247836ewiFJKS&*$^&#$JFIEfjdksljVLWEJKjdkfjkd'

Output:

['f', 'j', 's', 'd', 'l', 'k', 'a', 'j', 'l', 'v', 'e', 'w', 'i', 'F', 'J', 'K', 'S', 'J', 'F', 'I', 'E', 'f', 'j', 'd', 'k', 's', 'l', 'j', 'V', 'L', 'W', 'E', 'J', 'K', 'j', 'd', 'k', 'f', 'j', 'k', 'd']['4', '6', '3', '2', '4', '7', '8', '3', '6']['&', '*', '$', '^', '&', '#', '$']

Problem solving pattern

• Loop through the string by characters
• Check each character if it is the type of letters, digits or symbols.
• Return each list of result

String reverse

Requirements

Write a function to reverse a given string.

• Your are encouraged to use algorithms
• Not allowed to Python embedded reverse functions

Input:

string = "Children must be raught how to think, not what to think"

Output:

"kniht ot tahw ton ,kniht ot woh thguar eb tsum nerdlihC"

Problem solving pattern

• Step 1: Define a function with a parameter
• Step 2: Define a empty string variable
• Step 3: Loop through the string with for loop
• Step 4: Get the characters from the end until the beginning.
• Step 5: Add each character into the result string

Add suffix to string

Requirements

Given a string consists of different words end with ing. Write a function to append ly to words end with ing, and ing to those are not end with ing, ignore those already are end with ly.

• Not allowed to use Python endswith()
• You are encouraged to use algorithms

Input:

string = "He is fully absessed with eating. Eating and eating, don't stop forever!"

Output:

"Heing ising fully absesseding withing eatingly. Eatingly anding eatingly, don'ting stoping forever!ing"

Problem solving pattern

• Step 1: Write a function with a parameter
• Step 2: Loop through the string to get each word
• Step 3: Check if each word ends with ing or ly by splitting the word
• Step 4: Add each word appropriate suffix and return the result