stringstream in C++ and its Applications
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:
- clear()- To clear the stream.
- str()- To get and set string object whose content is present in the stream.
- operator <<- Add a string to the stringstream object.
- operator >>- Read something from the stringstream object.
Examples:
1. Count the number of words in a string
Examples:
Input: Asipu Pawan Kumar
Output: 3Input: 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; } |
Number of words are: 6
Time complexity: O(n*log(n)).
Auxiliary space: O(n).
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 -> 2Input: 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; } |
For-> 1 Geeks-> 2 Ide-> 1
Time complexity: O(n*log(n)).
Auxiliary space: O(n).
Removing spaces from a string using Stringstream
Converting Strings to Numbers in C/C++
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