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How to input a comma separated string in C++?

  • Difficulty Level : Hard
  • Last Updated : 23 Mar, 2021

Given an input string which is comma-separated instead of space, the task is to parse this input string in C++.
First, let us understand what difference does it create if the input string is comma-separated. 
Taking input a whitespace-separated string
Taking input a whitespace-separated string in C++ is very easy. The program to do so is:

C++




#include <bits/stdc++.h>
using namespace std;
 
int main()
{
    string str;
 
    // Get the string
    getline(cin, str);
 
    // Print the words
    cout << str;
}
Input: 
1 2 3 4 5 6

Output: 

1
2
3
4
5
6

 

Why can’t we use the above code for comma-separated input string? 
The above code works fine for a whitespace-separated input string, but for a comma-separated input string, it won’t work as expected, because the program will take complete input as a single word in the string.

Input: 



1, 2, 3, 4, 5, 6

Output: 

1, 2, 3, 4, 5, 6

 

How to input a comma separated string? 
Now inorder to input a comma separated string, following approach can be used: 

  1. Get the string to be taken as input in stringstream
  2. Take each character of the string one by one from the stream
  3. Check if this character is a comma (‘, ‘).
  4. If yes, then ignore that character.
  5. Else, Insert this character in the vector which stores the words

Below is the implementation of the above approach:

CPP




// C++ program to input
// a comma separated string
 
#include <bits/stdc++.h>
using namespace std;
 
int main()
{
    // Get the string
    string str = "11,21,31,41,51,61";
 
    vector<int> v;
 
    // Get the string to be taken
    // as input in stringstream
    stringstream ss(str);
 
    // Parse the string
    for (int i; ss >> i;) {
        v.push_back(i);
        if (ss.peek() == ',')
            ss.ignore();
    }
 
    // Print the words
    for (size_t i = 0; i < v.size(); i++)
        cout << v[i] << endl;
}
Output: 
11
21
31
41
51
61

 

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