Program to check if input is an integer or a string

2.7

Write a function to check whether a given input is an integer or a string.

Definition of an integer :

Every element should be a valid digit, i.e '0-9'.

Definition of a string :

Any one element should be an invalid digit, i.e any symbol other than '0-9'.

Examples:

Input : 127
Output : Integer
Explanation : All digits are in the range '0-9'.

Input : 199.7
Output : String
Explanation : A dot is present. 

Input : 122B
Output : String
Explanation : A alphabet is present.

The idea is to use isdigit() in C++.
Below is the C++ implementation :

// CPP program to check if a given string
// is a valid integer
#include <iostream>
using namespace std;

// Returns true if s is a number else false
bool isNumber(string s)
{
    for (int i = 0; i < s.length(); i++)
        if (isdigit(s[i]) == false)
            return false;

    return true;
}

// Driver code
int main()
{
    // Saving the input in a string
    string str = "6790";

    // Function returns 1 if all elements
    // are in range '0-9'
    if (isNumber(str))
        cout << "Integer";

    // Function returns 0 if the input is
    // not an integer
    else
        cout << "String";
}

Output:

Integer

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

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