Thread: Swapping surname......cont'd

Alright so about a week ago, we had a thread which asked about how to swap surname blahblahblah. Anyway the requirements were basically that you can't use the string library, nor create another array.

Well, we all had fun with this one on the C board, coming up with the shortest solution, ect. Anyway, I am up late, bored, not quite sober and decided to implement a generalized solution for a variable length input preserving whitespace formatting. Below is what I came up with; the problem is that this just doesn't feel like an "elegant" solution to me. Any pointers will be appreciated, thanks.

Code:

#include <iostream>
#include <iterator>
#include <algorithm>
#include <vector>


int main(){
	//Preserve whitespace formatting
	std::cin >> std::noskipws;
	
	//grab entire input buffer and store in vector
	std::istream_iterator<char>start(std::cin);
	std::istream_iterator<char>eos;
	std::vector<char>input(start,eos);

	//reverse vector
	std::reverse(input.begin(),input.end());
	
	//reverse "words" in vector based on whitespace
	std::vector<char>::iterator wordstart=input.begin()+1,
                                    spacepos=input.begin()+1;
	while(spacepos != input.end()){
		if(*spacepos==' '&&(*(spacepos-1)!=' ' || *(spacepos-1)!='\n'))
                {
			std::reverse(wordstart,spacepos);
			wordstart = spacepos+1;
		}
		++spacepos;
	}
	
	//output reversed input
	std::copy(input.begin(),
                  input.end(),
                  std::ostream_iterator<char>(std::cout));

	return (0);
}

Originally Posted by phantomotap

O_o

Are the names supposed to stay reversed?

Yes, in fact I was working on a generalized solution regardless of whitespace formatting and number of words entered.

Originally Posted by phantomotap

Anyway, you have a bug related to not fully reversing the last word.

Soma

Good catch, thanks. I forgot a line of code for the last word. Here is the updated solution. Still doesn't feel "right" to me. I do understand this is one of those "why would you do it" type of questions but it is more of a brainteaser kind of thing. Any additional comments, as always, are appreciated.

Code:

#include <iostream>
#include <iterator>
#include <algorithm>
#include <vector>


int main(){
	//Preserve whitespace formatting
	std::cin >> std::noskipws;
	
	//grab entire input buffer and store in vector
	std::istream_iterator<char>start(std::cin);
	std::istream_iterator<char>eos;
	std::vector<char>input(start,eos);

	//reverse vector
	std::reverse(input.begin(),input.end());
	
	//reverse "words"
	std::vector<char>::iterator wordstart=input.begin()+1,spacepos=input.begin()+1;
	while(spacepos != input.end()){
		if(*spacepos==' '&&(*(spacepos-1)!=' ' || *(spacepos-1)!='\n')){
			std::reverse(wordstart,spacepos);
			wordstart = spacepos+1;
		}
		++spacepos;
	}
	//reverse last word
	std::reverse(wordstart,spacepos);
	
	//output reversed input
	std::copy(input.begin(),input.end(),std::ostream_iterator<char>(std::cout));

	return (0);
}

Originally Posted by whiteflags

Might want to search the board: word reverser, not every idea is original.

I understand that, and thankyou for the advice. However, I was more or less trying to work within the confines of not using any string functions. I have coded a solution in C already that accomplishes this, as well as the solution above (the second one). I was just looking for some possible ideas as this one didn't seem elegant to me and I am more than aware that I am not familiar with every aspect of the STL.

Originally Posted by whiteflags

I think you can take C code and make it C++ code just by using strings, string iterators, and calling reverse. The actual code changes very little.

Oh, I see. My initial assumption for the problem is that no string functions can be used. I think you may have missed that.

Originally Posted by phantomotap

O_o

In that case, consider the "STL" functions `find_first_of' and friends.

And you still have a couple of bugs related to the last word.

Soma

I will take a look into that, thank you. Also for the bug, are you referring to how it treats the newline for multiple line input?