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Using return value of cin to take unknown number of inputs in C++
  • Difficulty Level : Easy
  • Last Updated : 13 Oct, 2017

Consider a problem where we need to take an unknown number of integer inputs.

A typical solution is to run a loop and stop when a user enters a particular value. How to do it if we are not allowed to use if-else, switch-case and conditional statement.

The idea is to use the fact that ‘cin >> input’ false if non-numertic value is given. Note that this above approach holds true only when input value’s data type is int (integer).

Important Point : cin is an object if std::istream. In C++11 and later, std::istream has a conversion function explicit bool() const;, meaning that there is a valid conversion from std::istream to bool, but only where explicitly requested. An if or while counts as explicitly requesting a conversion to bool. [Source StackOVerflow]
Before C++ 11, std::istream had a conversion to operator void*() const;





// CPP program to take unknown number
// of integers from user.
#include <iostream>
using namespace std;
int main()
    int input; 
    int count = 0; 
    cout << "To stop enter any character";
    cout << "\nEnter Your Input::";
    // cin returns false when a character
    // is entered
    while (cin >> input) 
    cout << "\nTotal number of inputs entered: " 
         << count;
    return 0;



To stop enter any character
Enter Your Input 1 2 3 s
Total number of inputs entered: 3

This article is contributed by Aditya Rakhecha. If you like GeeksforGeeks and would like to contribute, you can also write an article using or mail your article to See your article appearing on the GeeksforGeeks main page and help other Geeks.

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