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 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" ; } |
Java
// Java program to check if a given // string is a valid integer import 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 false def isNumber(s): for i in range ( len (s)): if s[i].isdigit() ! = True : return False return True # Driver code if __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 integer using 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 false function 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 type def isNumber(x): if type (x) = = int : return True else : return False # Driver Code input1 = 122 input2 = '122' # Function Call # for input1 if isNumber(input1): print ( "Integer" ) else : print ( "String" ) # for input2 if 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 integer import 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 the length of the string.
Auxiliary Space: O(1)
Method 4: Traverse and check if ASCII range falls under (0-9)
This method/algo is that traverse through the string and checks if ASCII range of every character falls under (0-9) or not. If every character is in range (48-57) then it prints that the string is an integer otherwise it is a string.
C++
// CPP program to check if a given string // is a valid integer #include <iostream> using namespace std; // Function to check if st is number or not bool isNumber(string st){ int i = 0; while (st[i] != NULL) { if (st[i] < 48 || st[i] > 57) return false ; i++; } return true ; } int main(){ // Saving the input in a string string st = "122B" ; // Function returns true if all elements are in // range '0-9' if (isNumber(st)) cout << "Integer" ; // Function returns false if the input is not an // integer, a string else cout << "String" ; return 0; } // This code is contributed by Susobhan Akhuli |
Java
import java.io.*; public class GFG { // Returns true if st is a number else false static boolean isNumber(String st) { for ( int i = 0 ; i < st.length(); i++) if (st.charAt(i) < 48 || st.charAt(i) > 57 ) return false ; return true ; } public static void main(String[] args) { // Saving the input in a string String st = "122B" ; // Function returns true if all elements are in // range '0-9' if (isNumber(st)) System.out.println( "Integer" ); // Function returns false if the input is not an // integer, a string else System.out.println( "String" ); } } // This code is contributed by Susobhan Akhuli |
C#
using System; public class Program { // Returns true if st is a number else false static bool isNumber( string st) { for ( int i = 0; i < st.Length; i++) if (st[i] < 48 || st[i] > 57) return false ; return true ; } static void Main( string [] args) { // Saving the input in a string string st = "122B" ; // Function returns true if all elements are in // range '0-9' if (isNumber(st)) Console.WriteLine( "Integer" ); // Function returns false if the input is not an // integer, a string else Console.WriteLine( "String" ); } } |
Javascript
// Javascript program to check if a given string // is a valid integer // Function to check if st is number or not function isNumber(st){ let i = 0; while (st[i] != null ) { if (st[i] < 48 || st[i] > 57) return false ; i++; } return true ; } // Saving the input in a string let st = "122B" ; // Function returns true if all elements are in // range '0-9' if (isNumber(st)) console.log( "Integer" ); // Function returns false if the input is not an // integer, a string else console.log( "String" ); |
String
Time Complexity: O(N) where N is the length of the string.
Auxiliary Space: O(1)
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