How to change the value of string from a cout - string

Question

void extractWord (string& str)
I have to write a function that extracts the word between ‘*’.
For example, using the three test cases below:
string s = "This is to be *reversed*"
string s1 ="*Reversed* starts here";
string s2 = "This is *in* the middle";
and after each function call,
s=reversed, s1=Reversed, s2=in
So i figured out...
void extractWord (string& str)
{
char target= '*';
int idx1=0;
while (str[idx1] != target)
idx1=idx1+1;
int idx2=idx1+1;
while (str[idx2] != target)
idx2=idx2+1;
for(int i=0;i<sizeof(str);i++)
{
if ((i>idx1)&&(i<idx2))
cout<<str[i];
}
}
int main()
{
string s="This is to be *reversed*";
string s1 = "*Reversed* starts here";
string s2= "This is *in* the middle";
extractWord(s);
cout<<endl;
extractWord(s1);
cout<<endl;
extractWord(s2);
cout<<endl;
}
but how do I change the value of s into the output of this function?

Answer 1

I have modified your code a bit. I hope this solves your problem:
//#include "stdafx.h"
#include < string >
#include < iostream >
using namespace std;
void extractWord (string& str)
{
char target= '*';
int idx1=0;
while (str[idx1] != target)
idx1=idx1+1;
int idx2=idx1+1;
while (str[idx2] != target)
idx2=idx2+1;
str=str.substr(idx1+1,idx2-idx1-1); //changed
}
int main()
{
string s="This is to be *reversed*";
string s1 = "*Reversed* starts here";
string s2= "This is *in* the middle";
extractWord(s);
cout<<s<<endl; //changed
extractWord(s1);
cout<<s1<<endl; //changed
extractWord(s2);
cout<<s2<<endl; //changed
system("PAUSE");
return 0;
}
Now, every time you call void extractWord (string& str) it replaces string with only word between *'s.
I've used std::string::substr function. > http://www.cplusplus.com/reference/string/string/substr/
Other option is to make function that returns word between *'s.
//#include "stdafx.h"
#include < string >
#include < iostream >
using namespace std;
string extractWord (string& str)
{
char target= '*';
int idx1=0;
while (str[idx1] != target)
idx1=idx1+1;
int idx2=idx1+1;
while (str[idx2] != target)
idx2=idx2+1;
return str.substr(idx1+1,idx2-idx1-1);
}
int main()
{
string s="This is to be *reversed*";
string s1 = "*Reversed* starts here";
string s2= "This is *in* the middle";
string res;
res=extractWord(s);
cout<<res<<endl;
res=extractWord(s1);
cout<<res<<endl;
res=extractWord(s2);
cout<<res<<endl;
system("PAUSE");
return 0;
}
However, note that it doesn't work if your string do not contain two *'s or it has more than one word that has to be extracted. I hope this helped you.