Information about stringstream

#1

hello sir , i wanted to know about this stringstream operator how it is working.
string reverseWords(string s) {
istringstream is(s);
string tmp;
is >> s;
cout <<s<<endl;
while(is >> tmp) s = tmp + " " + s;
if(s[0] == ’ ') s = “”;
return s;
}

#2

@khushi91200, can you send me the complete code using any ide , its not running correctly in my pc

#3

https://ide.codingblocks.com/s/285691 i tried but it si not running please see the error i am confused

#4

https://ide.codingblocks.com/s/285691 i tried but it is not running please see the error i am confused

#5

you did’nt include the header file i.e. #include < sstream >

#include <iostream>
#include <sstream>

using namespace std;

string reverseWords(string s) {
    istringstream is(s);
    string tmp;
    is >> s;
    while (is >> tmp) s = tmp + " " + s;
    if (s[0] == ' ') s = " ";
    return s;
}

int main()
{
    string s;
    getline(cin,s);
    cout << reverseWords(s) << endl;
    return 0;
}

this code works fine , let me explain how stringstream works , see to understand this you have to compare this with cin and cout , what stringstream do is it associates a string with a stream allowing you to read from the string as if it were a stream,like a continous flow of input (like cin ).when you enter a some words in the input you are passing a stream and what cin does is take words (space seperated) and adds the value to the corresponding variable using >> ,similarly here, we are creating an object is ,which acts like cin (as cin is an object of iostream class) it reads words until there is no word to read ,

if s is a sentence say , “How are you doing?” then is>>s will assign first word to s, i,e how , and the pointer will shift to next word , now we will enter in while loop which runs till end of input(similarly like while(cin>>s) ) tmp will contain “are” ,so s=are+" "+how, again pointer will shift to next word , is>>tmp will assign “you” to temp and now s=you+" "+"are how" , and finally we will have tmp as “doing?” making s as “doing? you are How”

this must be confusing if you don’t have much idea on streams and i/o using cin and cout ,
refer this to get more idea on stringstream


In case of any doubt feel free to ask :slight_smile:
Mark your doubt as RESOLVED if you got the answer

#6

@khushi91200
Is your doubt resolved?

#7

yes resolved thanks sir !!!

#8

sir one last thing can we do while(cin>>s) instead of while(is>>temp) will it work same?

#9

@khushi91200 Yes you can do that, check this https://ide.codingblocks.com/s/286027

#10

ok sir got it now !!!