Practice - Ordering strings based on summation of indices
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Practice Questions
Test your understanding with targeted questions
What is a countable set?
💡 Hint: Think about how you can count elements in a set.
Define an alphabet.
💡 Hint: What symbols can you think of in a language or code?
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Interactive Quizzes
Quick quizzes to reinforce your learning
What characterizes a countable set?
💡 Hint: Think about what it means to count an infinite set.
True or False: The set of all valid programs in a programming language is uncountable.
💡 Hint: Consider the finite nature of construction in programming.
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Challenge Problems
Push your limits with advanced challenges
Given an alphabet {d, e, f, g}, generate the strings of length 3 and explain how many valid sequences can be constructed.
💡 Hint: Think about the number of combinations of each letter.
Explain why the action of inserting a valid instruction into existing valid programs keeps the set of valid programs countable.
💡 Hint: Consider how each new insertion is still finite.
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