Given a string, the task is to check if that string contains any special character (defined special character set). If any special character found, don’t accept that string.
Examples :
Input : Geeks$For$Geeks
Output : String is not accepted.
Input : Geeks For Geeks
Output : String is accepted
Approach: Make a regular expression(regex) object of all the special characters that we don’t want, then pass a string in search method. If any one character of string is matching with regex object then search method returns a match object otherwise return None.
Below is the implementation :
C++
#include <iostream>
#include <regex>
using namespace std;
void run(string str)
{
regex regx("[@_!#$%^&*()<>?/|}{~:]");
if(regex_search(str, regx) == 0)
cout << "String is accepted";
else
cout << "String is not accepted.";
}
int main()
{
string str = "Geeks$For$Geeks";
run(str);
return 0;
}
|
Python3
import re
def run(string):
regex = re.compile('[@_!#$%^&*()<>?/\|}{~:]')
if(regex.search(string) == None):
print("String is accepted")
else:
print("String is not accepted.")
if __name__ == '__main__' :
string = "Geeks$For$Geeks"
run(string)
|
PHP
<?Php
function run($string)
{
$regex = preg_match('[@_!#$%^&*()<>?/\|}{~:]',
$string);
if($regex)
print("String is accepted");
else
print("String is not accepted.");
}
$string = 'Geeks$For$Geeks';
run($string);
?>
|
Java
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Main {
public static void main(String[] args)
{
String str = "Geeks$For$Geeks";
Pattern pattern
= Pattern.compile("[@_!#$%^&*()<>?/|}{~:]");
Matcher matcher = pattern.matcher(str);
if (!matcher.find()) {
System.out.println("String is accepted");
}
else {
System.out.println("String is not accepted");
}
}
}
|
C#
using System;
using System.Text.RegularExpressions;
class Program {
static void Run(string str)
{
Regex regex = new Regex("[@_!#$%^&*()<>?/|}{~:]");
if (!regex.IsMatch(str))
Console.WriteLine("String is accepted");
else
Console.WriteLine("String is not accepted.");
}
static void Main()
{
string str = "Geeks$For$Geeks";
Run(str);
Console.ReadLine();
}
}
|
OutputString is not accepted.
Method: To check if a special character is present in a given string or not, firstly group all special characters as one set. Then using for loop and if statements check for special characters. If any special character is found then increment the value of c. Finally, check if the c value is greater than zero then print string is not accepted otherwise print string is accepted.
C++
#include <iostream>
#include <string>
using namespace std;
int main() {
string n = "Geeks$For$Geeks";
int c = 0;
string s = "[@_!#$%^&*()<>?}{~:]";
for(int i = 0; i < n.size(); i++)
{
if (s.find(n[i]) != string::npos )
{
c++;
}
}
if(c){
cout << "string is not accepted" ;
}
else{
cout << "string is accepted";
}
return 0;
}
|
Java
import java.util.*;
class Main {
public static void main(String[] args)
{
String n = "Geeks$For$Geeks";
int c = 0;
String s = "[@_!#$%^&*()<>?}{~:]";
for (int i = 0; i < n.length(); i++) {
if (s.indexOf(n.charAt(i)) != -1) {
c++;
}
}
if (c > 0) {
System.out.println("string is not accepted");
}
else {
System.out.println("string is accepted");
}
}
}
|
Python3
n="Geeks$For$Geeks"
n.split()
c=0
s='[@_!#$%^&*()<>?/\|}{~:]' # special character set
for i in range(len(n)):
if n[i] in s:
c+=1
if c:
print("string is not accepted")
else:
print("string accepted")
|
Javascript
const n = "Geeks$For$Geeks";
let c = 0;
const s = "[@_!#$%^&*()<>?}{~:]";
for (let i = 0; i < n.length; i++) {
if (s.includes(n[i])) {
c++;
}
}
if (c) {
console.log("string is not accepted");
} else {
console.log("string is accepted");
}
|
Outputstring is not accepted
Using inbuilt methods:
Here is another approach to checking if a string contains any special characters without using regular expressions:
C++
#include <iostream>
#include <string>
using namespace std;
bool hasSpecialChar(string s) {
for (char c : s) {
if (!(isalpha(c) || isdigit(c) || c == ' ')) {
return true;
}
}
return false;
}
int main() {
string s = "Hello World";
if (hasSpecialChar(s)) {
cout << "The string contains special characters." << endl;
} else {
cout << "The string does not contain special characters." << endl;
}
s = "Hello@World";
if (hasSpecialChar(s)) {
cout << "The string contains special characters." << endl;
} else {
cout << "The string does not contain special characters." << endl;
}
return 0;
}
|
Python3
def has_special_char(s):
for c in s:
if not (c.isalpha() or c.isdigit() or c == ' '):
return True
return False
s = "Hello World"
if has_special_char(s):
print("The string contains special characters.")
else:
print("The string does not contain special characters.")
s = "Hello@World"
if has_special_char(s):
print("The string contains special characters.")
else:
print("The string does not contain special characters.")
|
Java
class Main {
public static boolean hasSpecialChar(String s)
{
for (int i = 0; i < s.length(); i++) {
char c = s.charAt(i);
if (!(Character.isLetterOrDigit(c)
|| c == ' ')) {
return true;
}
}
return false;
}
public static void main(String[] args)
{
String s1 = "Hello World";
if (hasSpecialChar(s1)) {
System.out.println(
"The string contains special characters.");
}
else {
System.out.println(
"The string does not contain special characters.");
}
String s2 = "Hello@World";
if (hasSpecialChar(s2)) {
System.out.println(
"The string contains special characters.");
}
else {
System.out.println(
"The string does not contain special characters.");
}
}
}
|
OutputThe string does not contain special characters.
The string contains special characters.
This approach uses the isalpha() and isdigit() methods to check if a character is an alphabetical character or a digit, respectively. If a character is neither an alphabetical character nor a digit, it is considered a special character.
The time complexity of this function is O(n), where n is the length of the input string, because it involves a single loop that iterates through all the characters in the string.
The space complexity of this function is O(1), because it does not use any additional data structures and the space it uses is independent of the input size.
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