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Size doesn't really matters...right?

Marcus · 2017-10-06T14:51:50

I was completing a challenge on codefights, the challenge was: Quote Given a string, find the shortest possible string which can be achieved by adding characters to the end of initial string to make it a palindrome. Example For st = "abcdc", the output should bebuildPalindrome(st) = "abcdcba". Below my solution and the top rated solution: MySolution: string buildPalindrome(string str) { auto BeginIt = str.begin(); auto EndIt = str.end() - 1; bool IsAlreadyPalindrome = true; for (; BeginIt < EndIt; BeginIt++, EndIt--) { if (*BeginIt != *EndIt) { EndIt = str.end(); IsAlreadyPalindrome = false; } } //case midpoint not found if (BeginIt != EndIt) { //case is a palindrome if (IsAlreadyPalindrome) { return str; } //case not a palindrome, no midpoint if (str[str.size() - 1] == str[str.size() - 2]) { string HalfStr(str.substr(0, BeginIt - str.begin())); return string(HalfStr + string(HalfStr.rbegin(), HalfStr.rend())); } } //case not a palindrome, with midpoint auto MidIt = BeginIt != EndIt? str.end() - 1: BeginIt; string HalfStr(str.substr(0, MidIt - str.begin())); return string(HalfStr + *MidIt + string(HalfStr.rbegin(), HalfStr.rend())); } TopRatedSolution: std::string buildPalindrome(std::string st) { string ret(st); auto it = st.begin(); while (ret != string(ret.rbegin(), ret.rend())) { ret.insert(st.size(), 1, *it++); } return ret; } Now, when I completed the challenge and checked others solution I was a bit discouraged to see that it could be completed in so few lines and took me so many, but then out of curiosity I timed it online against mine with an impossibly long string, while the top rated took 13sec to solve it mine took 0,33sec... Now I'm pretty sure mine won't ever get a single vote because it looks ugly to see (too many lines). Now I'm not saying mine is better (now after solving I see 2 things that could be easily improved also), I realize that readability is important and such a function won't ever be used with strings that long, so my performance gain was pretty much pointless in all real contexts (and also accidental by the way, I was just trying to solve the challenge in the most straightforward way I could see), though I am kind of disappointed by the fact that a site about challenging others and improving, made by hundreds of programmers is "celebrating" something as empty/meaningless as "number of lines used" over readability or performance... I mean, couldn't that site have users voting on readability and a scoring given by the site based on performances?! I'm not a fan of that mentality of "watch how hacky I am, can solve it in 0 lines" if then is not readable and the performance are atrocious (not saying is the case with all the short solutions btw), I should probably just start avoiding that place because with that goals/highlights in mind, seems like a good way to train bad programmers in mass to me... Anyway, just my rant because I'm still disappointed it took me so many lines What's your opinion on this? Shouldn't sites like that hold to higher standards?

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Started by MarcusAseth October 05, 2017 06:19 AM

54 comments, last by JoeJ 6 years, 9 months ago

matt77hias

560

October 06, 2017 01:02 PM

8 minutes ago, MarcusAseth said:

seriously, I don't know nor care for C++98, this other aproach won't work... whatever the point you're trying to make is, you're only obfuscating it more...

C++98 is just the 1st C++ standard.

C++11/14 are two recent standards (3th and 4th, respectively) which differentiate between lvalues and rvalues.

C++98 already supported assignment operators. The compiled C++98 code of all the code snippets in this topic would do exactly the same as C++11/14 code (backwards compatibility). So you do not use or exploit any new feature of C++11/14. So you cannot (wrongly) use lvalue/rvalue argumentation because it clearly is independent of lvalues/rvalues. It has nothing to do with lvalues/rvalues like I said. It is just implicit constness.

If you won't believe this, go to http://cpp.sh/ and select C++98 for compilation.

🧙

MarcusAseth

Author

October 06, 2017 01:11 PM

And why are you blindly assuming my point is exploiting some nifty trick of C++ 11/14?!

I went and checked the C++ draft from the 97, and the quote I posted in the page before was already there at the time.

At this point I don't see any point in keep arguing, because you are simply not even considering the proof I'm showing you.

My portfolio: https://www.artstation.com/artist/marcusaseth

MarcusAseth

Author

October 06, 2017 01:17 PM

15 minutes ago, matt77hias said:

C++98 is just the 1st C++ standard.

C++11/14 are two recent standards (3th and 4th, respectively) which differentiate between lvalues and rvalues.

And this is completely wrong.

C++98 differentiate between lvalue and rvalue, in C++ 11 and 14 there is simply more differentiation(6 categories or something)

Clearly you are confused in this and are not putting a serious effort to read the proof I show you or to reason together about it (meaning you have already decided what you want to believe), so I won't continue to try and convince you.

My portfolio: https://www.artstation.com/artist/marcusaseth

JoeJ

4,266

October 06, 2017 02:38 PM

Maybe it helps to differentiate between string and int: String is a class or struct, while int is... primitive or built in type? Not sure about terminology.

JoeJ

4,266

October 06, 2017 02:51 PM

3 hours ago, MarcusAseth said:
Why this code below compiles:
string f(string& n)
{
	return n += "99";
}

int main() {
	string a = "";
	string b = "!!!";
	
	f(a) = b;//COMPILE
}
While the one below doesnt?
int f(int& n)
{
	return n += 99;
}

int main()
{
	int a = 1;
	int b = 7;

	f(a) = b;//WON'T COMPILE
}
Both functions return by value and take an argument by reference.

The first example makes little sense, but a will be "99", and b "!!!"

The second example makes no sense, because the returned value from f does not exist (because you don't use it, compiler does not create it), so you can't assign b to it.

Back to the first example, here the compiler could create a temporary string "!!!" and remove it, or be clever and do nothing.

The difference is only that int is a "built in type?" that can live in registers, but a string can only live in memory because it does not fit inside a register.

... guess that's it but i'm no expert (some programmers have little interest in programming languages itself).

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Size doesn't really matters...right?

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