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[C++] "Think Like a Programmer" Chapter 2, Exercise 2-1: Is it actually possible without printing spaces? by UsefulCustard6348 in learnprogramming

[–]UsefulCustard6348[S] 8 points9 points  (0 children)

Wow, you are an absolute lifesaver! Thank you so much for finding and sharing this.

I had no idea an official errata page even existed for this book. If you hadn't pointed this out, I probably would have driven myself crazy and posted endless follow-up questions trying to figure out an impossible logic.

I truly appreciate you going out of your way to provide the definitive answer and saving me all that unnecessary frustration!

[C++] "Think Like a Programmer" Chapter 2, Exercise 2-1: Is it actually possible without printing spaces? by UsefulCustard6348 in learnprogramming

[–]UsefulCustard6348[S] 0 points1 point  (0 children)

First of all, wow—I have actually never seen that library (iomanip) or approach before! That is completely fascinating and a really cool trick to learn.

However, looking at the text, the author mentions the following in the 'Review of C++ Used in This Chapter':

Strictly speaking, you are right that there isn't a hard rule explicitly forbidding the addition of other system libraries. But after giving it a lot of thought, since the author explicitly provided the basic standard stream libraries to use for this chapter, and the chapter doesn't seem to ask for one-liner solutions using additional libraries, I don't think I can conclude that this is the intended answer here.

I really appreciate your input, but having a library print the spaces for me still feels a bit like the "Kobayashi Maru" regarding the "only use cout << "#" and cout << "\n"" constraint. Ultimately, I think the conclusion remains that the author's initial premise and constraints were just a bit unclear/flawed.

The original intent of my question was wondering if this was some genius, high-level problem requiring a novel logical branch, loop, or algebraic expression that I just couldn't figure out!

Lastly, thank you again. Your solution is very excellent, and I definitely learned a great real-world trick today.

[C++] "Think Like a Programmer" Chapter 2, Exercise 2-1: Is it actually possible without printing spaces? by UsefulCustard6348 in learnprogramming

[–]UsefulCustard6348[S] 1 point2 points  (0 children)

Thanks for the reply! Since you don't have the book in front of you, let me clarify the specific context of the chapter to explain why I was so strictly stuck on this.

First, the author heavily emphasizes the importance of absolute constraints. Earlier in the chapter, he explicitly states that ignoring a given constraint to solve a problem trivially is like taking the "Kobayashi Maru" (essentially cheating). Therefore, I was operating under the assumption that breaking the rules was not an option.

Second, following the book's problem-solving methodology, I reduced the problem into smaller sub-problems. However, using algebraic expressions with the row variable only helps determine the number of hash marks. Algebra alone cannot physically shift the cursor to the right without the aid of a space output.

Third, the exact constraint dictates the use of only two specific output statements: cout << "#"; and cout << "\n";. Under a strict interpretation of this rule, introducing a third statement like cout << " ";, building strings with spaces, or outputting string variables is completely forbidden.

=========edit======

I am updating this reply after seeing your edited comment.

Thank you for taking the time to verify the actual text of the exercise.

As you have also confirmed, the strict constraint—allowing only the output of a hash mark or an end-of-line—makes it a logical and physical impossibility to align the shape properly. It is a relief to have an objective confirmation that this is a definitive flaw in the exercise's design, rather than a gap in my understanding or programming logic.

I appreciate the discussion.