Read String
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Hi I want to find the number of comma(,) in particular string. Like char* str = "a,b,c,d,e". So how many commas are there in str ? Thanks
Use
strchrin a loop.char* str = "a,b,c,d,e";
int count = 0;for (;;)
{
str = strchr(str, ',');
if (NULL == str)
break;++str; ++count;}
«_Superman_»
I love work. It gives me something to do between weekends. -
Hi I want to find the number of comma(,) in particular string. Like char* str = "a,b,c,d,e". So how many commas are there in str ? Thanks
std::count is your friend. It does exactly what you'd expect it to do from it's name. The only problem you're likely to have is working out where the end of the characters in memory are, but if you're feeling lazy bung the characters in a std::string first:
std::string s( str );
std::cout << "There are " << std::count( s.begin(), s.end(), ',' ) << " commas in " << s << std::endl;Cheers, Ash
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Hi I want to find the number of comma(,) in particular string. Like char* str = "a,b,c,d,e". So how many commas are there in str ? Thanks
char c;
int commas=0;
while((c=*str++)!=0) if (c==',') commas++;:)
Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles] Nil Volentibus Arduum
Please use <PRE> tags for code snippets, they preserve indentation, and improve readability.
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Hi I want to find the number of comma(,) in particular string. Like char* str = "a,b,c,d,e". So how many commas are there in str ? Thanks
const char \*p = "a,b,c,de,f,"; int c = 0; for (;\*p;c+=(','==\*p++)); -
const char \*p = "a,b,c,de,f,"; int c = 0; for (;\*p;c+=(','==\*p++));Ahh, the joys of C++. Did you make it so complex on purpose, or is all your code written like that ? ;P
Cédric Moonen Software developer
Charting control [v3.0] OpenGL game tutorial in C++ -
Hi I want to find the number of comma(,) in particular string. Like char* str = "a,b,c,d,e". So how many commas are there in str ? Thanks
[Untested]:
std::string str("a, b, c, d, e");
int count = std::count(str.begin(), str.end(), ',');or if you insist on C-style strings:
int count = std::count(str, str + strlen(str), ',');
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Hi I want to find the number of comma(,) in particular string. Like char* str = "a,b,c,d,e". So how many commas are there in str ? Thanks
The inline ASM version is still missing, anyone? :D
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The inline ASM version is still missing, anyone? :D
I think is interesting to compare the solutions. Note: The "trivial" algorithm is to scan the string and count the ','. Now: Superman: Just did that using CRT: no additional data are added, and the strchr function is made walking from ',' to ','. Aescleal: Made an elegant use of STL algorithms. But: a constant literal is copied into a temporary std::string (probably with also a dynamic array allocated by the class itself), creates two temporary iterators, passing them to the std::count algorithm that just do the loop. Luc Pattyn: Use a more concise loop. Chris Losinger: same. Very elegant, but more cryptic. Nemanja Trifunovich: Same a Aescleal, but also propose to use std::cout with
const char*instead ofstd::string::iterator-s, eliminating the need of the conversions. Moral of the story: I'm starting to believe that STL - and in particular "strings" are over-evaluated. The more coincise and elegant (together) is probably the second Nemanja proposal. But one question makes me wonder: Suppose I'm a coder asked to do this task, and suppose I know the algoritm, but i'm not expert in the language libraries: what should be fastest for me? - Read the STL documentation -probaly in strict alphabetic order- trying to guess is there can be something that can help me in counting the ',' (I'm luky the <algorithm> header come as first and the count function is one of the firsts ... estimated time: 15 minutes - but supposing I already know the "iterator"/"container"/"algorithm" model) - Just writeunsigned count_chars(const char* s, char d)
{
unsigned c=0;
for(unsigned int i=0; s[i]; ++i)
if(s[i]==d) ++c;
return c;
}actual time 2 minutes! And the best of efficiency (no spurious allocation and copies)
<sarcasm>Do yo understand the beauty of STL ?!?</sarcasm>(NOTE: using indexes, instead of incrementing pointers, is actually more efficient when translated into todays processor's code)2 bugs found. > recompile ... 65534 bugs found. :doh:
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I think is interesting to compare the solutions. Note: The "trivial" algorithm is to scan the string and count the ','. Now: Superman: Just did that using CRT: no additional data are added, and the strchr function is made walking from ',' to ','. Aescleal: Made an elegant use of STL algorithms. But: a constant literal is copied into a temporary std::string (probably with also a dynamic array allocated by the class itself), creates two temporary iterators, passing them to the std::count algorithm that just do the loop. Luc Pattyn: Use a more concise loop. Chris Losinger: same. Very elegant, but more cryptic. Nemanja Trifunovich: Same a Aescleal, but also propose to use std::cout with
const char*instead ofstd::string::iterator-s, eliminating the need of the conversions. Moral of the story: I'm starting to believe that STL - and in particular "strings" are over-evaluated. The more coincise and elegant (together) is probably the second Nemanja proposal. But one question makes me wonder: Suppose I'm a coder asked to do this task, and suppose I know the algoritm, but i'm not expert in the language libraries: what should be fastest for me? - Read the STL documentation -probaly in strict alphabetic order- trying to guess is there can be something that can help me in counting the ',' (I'm luky the <algorithm> header come as first and the count function is one of the firsts ... estimated time: 15 minutes - but supposing I already know the "iterator"/"container"/"algorithm" model) - Just writeunsigned count_chars(const char* s, char d)
{
unsigned c=0;
for(unsigned int i=0; s[i]; ++i)
if(s[i]==d) ++c;
return c;
}actual time 2 minutes! And the best of efficiency (no spurious allocation and copies)
<sarcasm>Do yo understand the beauty of STL ?!?</sarcasm>(NOTE: using indexes, instead of incrementing pointers, is actually more efficient when translated into todays processor's code)2 bugs found. > recompile ... 65534 bugs found. :doh:
An interesting comparison, Emilio! My two cents. I think someone who has encountered this kind of problem before (data manipulation, string parsing) will need the equal amount of time for either a handcoded C-string solution (e.g. Luc's) or using a library solution (e.g. Aescleal's). Let's say 1 minute. Someone who does it the first time, would probably do the same as when I write something in a new language, you Google for examples and then use the first code snippet you like (probably it's not the best solution but a working one). Let's say 5 minutes. Cheers, M PS: The beauty of STL glows in less trivial examples. The iterator design pattern in particular is a nice idea in my opinion, it gives you a decoupling of data object and algorithm, e.g. you can use the same algorithm with a wide range of objects... and only have to learn it once = time saved.
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Ahh, the joys of C++. Did you make it so complex on purpose, or is all your code written like that ? ;P
Cédric Moonen Software developer
Charting control [v3.0] OpenGL game tutorial in C++That was classic Kernighan and Richie C! Sheesh, youngsters of today... Whippersnapper! Iain.
I am one of "those foreigners coming over here and stealing our jobs". Yay me!
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An interesting comparison, Emilio! My two cents. I think someone who has encountered this kind of problem before (data manipulation, string parsing) will need the equal amount of time for either a handcoded C-string solution (e.g. Luc's) or using a library solution (e.g. Aescleal's). Let's say 1 minute. Someone who does it the first time, would probably do the same as when I write something in a new language, you Google for examples and then use the first code snippet you like (probably it's not the best solution but a working one). Let's say 5 minutes. Cheers, M PS: The beauty of STL glows in less trivial examples. The iterator design pattern in particular is a nice idea in my opinion, it gives you a decoupling of data object and algorithm, e.g. you can use the same algorithm with a wide range of objects... and only have to learn it once = time saved.
Moak wrote:
The beauty of STL glows in less trivial examples
Oh yes ... but reality is different: it is a matter of fact that vector (sequential indexed), list (sequential) and map (indexed) don't have same interfaces, and that the most of stl algorithm that are "non trivial" works with "sequential indexed" (aka "random access") iterators. Two siple example:
std::list<int> alist;
std::vector<int> avector;alist.remove(10); //remove all 10s
avector.erase(std::remove(avector.begin(),avector.end(),10),avector.end());Until someone doesn't demonstrate me how can I come to write the second example without having the knowledge of at least 20 pages of documentation (yes, I want a 8 y.o. baby coding that!), I will consider "you can use the same algorithm with a wide range of objects... and only have to learn it once = time saved." a pure marketing lye. (The fake is that
vectordoesn't have aremovefunction, hence is not dual tolist, andstd::removedoesn't remove: it just swaps things around. You cannot know that unless someone tells you) The pattern itself can be a good idea (iterators as a bridge between collections and algorithms) but the way is implemented is far from being obvious. That's the point i was considering.2 bugs found. > recompile ... 65534 bugs found. :doh:
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Moak wrote:
The beauty of STL glows in less trivial examples
Oh yes ... but reality is different: it is a matter of fact that vector (sequential indexed), list (sequential) and map (indexed) don't have same interfaces, and that the most of stl algorithm that are "non trivial" works with "sequential indexed" (aka "random access") iterators. Two siple example:
std::list<int> alist;
std::vector<int> avector;alist.remove(10); //remove all 10s
avector.erase(std::remove(avector.begin(),avector.end(),10),avector.end());Until someone doesn't demonstrate me how can I come to write the second example without having the knowledge of at least 20 pages of documentation (yes, I want a 8 y.o. baby coding that!), I will consider "you can use the same algorithm with a wide range of objects... and only have to learn it once = time saved." a pure marketing lye. (The fake is that
vectordoesn't have aremovefunction, hence is not dual tolist, andstd::removedoesn't remove: it just swaps things around. You cannot know that unless someone tells you) The pattern itself can be a good idea (iterators as a bridge between collections and algorithms) but the way is implemented is far from being obvious. That's the point i was considering.2 bugs found. > recompile ... 65534 bugs found. :doh:
Please have a breakfast before making angry morning postings. :)