strings

kathrine (11)
Q1:-The user enters a sentence your task is to output every word on a new line.
*please note that i haven't learnt strings yet so please help me with it.* 
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 #include<iostream>
#include<string>
using namespace std;
int main(){

    cout<<"enter your sentence"<<endl;
    string a;
    getline(cin,a);

 int b=a.length();
    for(int i=0;i<b;i++){

       if(a==" ")
        cout<<endl;
        else
           cout<<a.substr(i,b);
    }
return 0;}
cire (8284)
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#include <iostream>
#include <string>

int main()
{
    while (std::cin.peek() != '\n')
    {
        std::string word ;
        std::cin >> word ;
        std::cout << word << '\n' ;
    }
}


Of course, you can fool that piece of code by not ending a sentence with a newline, for instance by entering a space then a newline at the termination of a sentence, thereby causing the loop to continue past the point where it should stop.

Making a helper function or two to advance to the next word in the sentence might help:

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#include <iostream>
#include <string>
#include <cctype>

bool nextIsWhitespace(std::istream& is)
{
    int ch = is.peek() ;

    if ( ch == std::char_traits<std::istream::char_type>::eof() )
    {
        is.get(); // set eof flag
        return false ;
    }

    return std::isspace(static_cast<unsigned char>(ch)) ;
}

bool nextWord(std::istream& is)
{
    while ( nextIsWhitespace(is) && is.peek() != '\n' )
        is.ignore() ;

    bool isNextWord = is && is.peek() != '\n' ;

    if ( !isNextWord )
        is.ignore() ;

    return isNextWord ;
}

int main()
{
    do
    {
        std::string word ;
        std::cin >> word ;
        std::cout << word << '\n' ;
    } while ( nextWord(std::cin) ) ;
}


Alternately, one might take advantage of stringstreams:

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#include <iostream>
#include <string>
#include <sstream>

int main()
{
    std::cout << "Enter a sentence.\n" ;
    std::string sentence ;
    std::getline(std::cin, sentence) ;

    std::istringstream wordstream(sentence) ;

    std::string word ;
    while ( wordstream >> word )
        std::cout << word << '\n' ;
}


Come to think of it, there may be a few more ways to do this.
ats15 (423)
One easy way is to replace white spaces with new lines. Note that if you have space space, then the output will contain an empty line

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#include<iostream>
#include<string>

using namespace std;
int main()
{
    cout<<"enter your sentence"<<endl;
    string a;
    getline(cin,a);

    for(int i=0;i<a.length();i++)
   {
       if(a[i]==" ") a[i]='\n';
    }
   cout<<a<<endl;
   return 0;
}
kathrine (11)
@ats15 the code doesn't work it says that you can't compare integer and pointers in if loop. what should i do?
cire (8284)
You might change line 13 to read:

if (a[i]==' ')...
kathrine (11)
thank you it makes sense now...:)
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