Program to check if input is an integer or a string
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.
Method 1: The idea is to use isdigit() function and is_numeric() function..
Below is the implementation of the above idea.
C++
// 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 falsebool isNumber(string s){ for (int i = 0; i < s.length(); i++) if (isdigit(s[i]) == false) return false; return true;}// Driver codeint 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";} |
Java
// Java program to check if a given// string is a valid integerimport java.io.*;public class GFG { // Returns true if s is // a number else false static boolean isNumber(String s) { for (int i = 0; i < s.length(); i++) if (Character.isDigit(s.charAt(i)) == false) return false; return true; } // Driver code static public void main(String[] args) { // Saving the input in a string String str = "6790"; // Function returns 1 if all elements // are in range '0 - 9' if (isNumber(str)) System.out.println("Integer"); // Function returns 0 if the // input is not an integer else System.out.println("String"); }}// This code is contributed by vt_m. |
Python 3
# Python 3 program to check if a given string# is a valid integer# This function Returns true if# s is a number else falsedef isNumber(s): for i in range(len(s)): if s[i].isdigit() != True: return False return True# Driver codeif __name__ == "__main__": # Store the input in a str variable str = "6790" # Function Call if isNumber(str): print("Integer") else: print("String")# This code is contributed by ANKITRAI1 |
C#
// C# program to check if a given// string is a valid integerusing System;public class GFG { // Returns true if s is a // number else false static bool isNumber(string s) { for (int i = 0; i < s.Length; i++) if (char.IsDigit(s[i]) == false) return false; return true; } // Driver code static public void Main(String[] args) { // Saving the input in a string string str = "6790"; // Function returns 1 if all elements // are in range '0 - 9' if (isNumber(str)) Console.WriteLine("Integer"); // Function returns 0 if the // input is not an integer else Console.WriteLine("String"); }}// This code is contributed by vt_m. |
PHP
<?php// PHP program to check if a// given string is a valid integer// Returns true if s// is a number else falsefunction isNumber($s){ for ($i = 0; $i < strlen($s); $i++) if (is_numeric($s[$i]) == false) return false; return true;}// Driver code// Saving the input// in a string$str = "6790";// Function returns// 1 if all elements// are in range '0-9'if (isNumber($str)) echo "Integer";else echo "String";// This code is contributed by ajit?> |
Javascript
<script> // Javascript program to check if a given // string is a valid integer // Returns true if s is a // number else false function isNumber(s) { for (let i = 0; i < s.length; i++) if (s[i] < '0' || s[i] > '9') return false; return true; } // Saving the input in a string let str = "6790"; // Function returns 1 if all elements // are in range '0 - 9' if (isNumber(str)) document.write("Integer"); // Function returns 0 if the // input is not an integer else document.write("String"); </script> |
Integer
Time Complexity: O(n)
Auxiliary Space: O(1)
Method 2: Using special Python built-in type() function:
type() is a built-in function provided by python . type() takes object as parameter and returns its class type as its name says.
Below is the implementation of the above idea:
Python3
# Python program to find# whether the user input# is int or string type# Function to determine whether# the user input is string or# integer typedef isNumber(x): if type(x) == int: return True else: return False# Driver Codeinput1 = 122input2 = '122'# Function Call# for input1if isNumber(input1): print("Integer")else: print("String")# for input2if isNumber(input2): print("Integer")else: print("String") |
Integer String
Time Complexity: O(1)
Auxiliary Space: O(1)
Method 3: Using Integer.parseInt() in Java
The parseInt() method of Integer class is used to parse a given string into an integer provided that the string contains a valid integer. In case, the string doesn’t contain a valid integer, it throws a NumberFormatException. The idea is to parse the given string using the same. If an exception is found, then the given string will not be a valid integer and vice-versa.
Below is the implementation of the above idea:
Java
// Java program to check if a given// string is a valid integerimport java.io.*;public class GFG { // Driver code static public void main(String[] args) { String s = "abc"; //sample input to test try{ Integer.parseInt(s); System.out.println("Integer"); }catch(NumberFormatException e){ System.out.println("String"); } }}// This code is contributed by shruti456rawal |
String
Time Complexity: O(N) where N is length of string.
Auxiliary Space: O(1)
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