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stringstream in C++ and its applications

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  • Difficulty Level : Medium
  • Last Updated : 30 Jan, 2022

A stringstream associates a string object with a stream allowing you to read from the string as if it were a stream (like cin). To use stringstream, we need to include sstream header file. The stringstream class is extremely useful in parsing input. 

Basic methods are:

  1. clear()- To clear the stream.
  2. str()- To get and set string object whose content is present in the stream. 
  3. operator <<- Add a string to the stringstream object. 
  4. operator >>- Read something from the stringstream object.

Examples:

1. Count the number of words in a string-

Examples-

Input: Asipu Pawan Kumar
Output: 3

Input: Geeks For Geeks Ide
Output: 4

Below is the C++ program to implement the above approach-

C++




// C++ program to count words in 
// a string using stringstream.
#include <iostream>
#include <sstream>
#include<string>
using namespace std;
 
int countWords(string str)
{
    // Breaking input into word
    // using string stream
   
    // Used for breaking words
    stringstream s(str);
   
    // To store individual words
    string word;
 
    int count = 0;
    while (s >> word)
        count++;
    return count;
}
 
// Driver code
int main()
{
    string s = "geeks for geeks geeks "
               "contribution placements";
    cout << " Number of words are: " << countWords(s);
    return 0;
}


Output

 Number of words are: 6

2. Print frequencies of individual words in a string-

Examples-

Input: Geeks For Geeks Quiz Geeks Quiz Practice Practice
Output: For -> 1
             Geeks -> 3
             Practice -> 2
             Quiz -> 2

Input: Word String Frequency String
Output: Frequency -> 1
              String -> 2
              Word -> 1     

Below is the C++ program to implement the above approach-

C++




// C++ program to demonstrate use
// of stringstream to count
// frequencies of words.
#include <bits/stdc++.h>
#include <iostream>
#include <sstream>
#include<string>
using namespace std;
 
void printFrequency(string st)
{
    // Each word it mapped to
    // it's frequency
    map<string, int>FW;
   
    // Used for breaking words
    stringstream ss(st);
   
    // To store individual words
    string Word;
 
    while (ss >> Word)
        FW[Word]++;
 
    map<string, int>::iterator m;
    for (m = FW.begin(); m != FW.end(); m++)
        cout << m->first << "-> "
             << m->second << "\n";
}
 
// Driver code
int main()
{
    string s = "Geeks For Geeks Ide";
    printFrequency(s);
    return 0;
}


Output

For-> 1
Geeks-> 2
Ide-> 1

3. Removing spaces from a string using Stringstream
4. Converting Strings to Numbers in C/C++

This article is contributed by ASIPU PAWAN KUMAR. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.


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