Check if a string consists only of special characters

Given string str of length N, the task is to check if the given string contains only special characters or not. If the string contains only special characters, then print “Yes”. Otherwise, print “No”.

Examples:

Input: str = “@#$&%!~”
Output: Yes
Explanation: 
Given string contains only special characters. 
Therefore, the output is Yes.

Input: str = “Geeks4Geeks@#”
Output: No
Explanation: 
Given string contains alphabets, number, and special characters. 
Therefore, the output is No.

Naive Approach: Iterate over the string and check if the string contains only special characters or not. Follow the steps below to solve the problem:

• Traverse the string and for each character, check if its ASCII value lies in the ranges [32, 47], [58, 64], [91, 96] or [123, 126]. If found to be true, it is a special character.
• Print Yes if all characters lie in one of the aforementioned ranges. Otherwise, print No.

Time Complexity: O(N)
Auxiliary Space: O(1)

Space-Efficient Approach: The idea is to use Regular Expression to optimize the above approach. Follow the steps below:

• Create the following regular expression to check if the given string contains only special characters or not.

regex = “[^a-zA-Z0-9]+”

where,

• [^a-zA-Z0-9] represents only special characters.
• + represents one or more times.

• Match the given string with the Regular Expression using Pattern.matcher() in Java
• Print Yes if the string matches with the given regular expression. Otherwise, print No.

Below is the implementation of the above approach:

// C++ program to check if the string
// contains only special characters
#include <iostream>
#include <regex>
using namespace std;

// Function to check if the string contains only special characters.
void onlySpecialCharacters(string str)
{

  // Regex to check if the string contains only special characters.
  const regex pattern("[^a-zA-Z0-9]+");


  // If the string
  // is empty then print "No"
  if (str.empty())
  {
     cout<< "No";
     return ;
  }

  // Print "Yes" if the string contains only special characters
  // matched the ReGex
  if(regex_match(str, pattern))
  {
    cout<< "Yes";
  }
  else
  {
    cout<< "No";
  }
}

// Driver Code
int main()
{
  
  // Given string str
  string str = "@#$&%!~";
  onlySpecialCharacters(str) ;

  return 0;
}

// This code is contributed by yuvraj_chandra

// Java program to check if the string
// contains only special characters

import java.util.regex.*;
class GFG {

    // Function to check if a string
    // contains only special characters
    public static void onlySpecialCharacters(
        String str)
    {

        // Regex to check if a string contains
        // only special characters
        String regex = "[^a-zA-Z0-9]+";

        // Compile the ReGex
        Pattern p = Pattern.compile(regex);

        // If the string is empty
        // then print No
        if (str == null) {
            System.out.println("No");
            return;
        }

        // Find match between given string
        // & regular expression
        Matcher m = p.matcher(str);

        // Print Yes If the string matches
        // with the Regex
        if (m.matches())
            System.out.println("Yes");
        else
            System.out.println("No");
    }

    // Driver Code
    public static void main(String args[])
    {
        // Given string str
        String str = "@#$&%!~";

        // Function Call
        onlySpecialCharacters(str);
    }
}

# Python program to check if the string
# contains only special characters
import re

# Function to check if a string
# contains only special characters
def onlySpecialCharacters(Str):

    # Regex to check if a string contains
    # only special characters
    regex = "[^a-zA-Z0-9]+"

    # Compile the ReGex
    p=re.compile(regex)

    # If the string is empty
    # then print No
    if(len(Str) == 0):
        print("No")
        return

    # Print Yes If the string matches
    # with the Regex
    if(re.search(p, Str)):
        print("Yes")
    else:
        print("No")

# Driver Code

# Given string str
Str = "@#$&%!~"

# Function Call
onlySpecialCharacters(Str)

# This code is contributed by avanitrachhadiya2155

// C# program to check if 
// the string contains only 
// special characters
using System;
using System.Text.RegularExpressions;  
class GFG{

// Function to check if a string
// contains only special characters
public static void onlySpecialchars(String str)
{
  // Regex to check if a string 
  // contains only special 
  // characters
  String regex = "[^a-zA-Z0-9]+";

  // Compile the ReGex
  Regex rgex = new Regex(regex);  

  // If the string is empty
  // then print No
  if (str == null) 
  {
    Console.WriteLine("No");
    return;
  }

  // Find match between given 
  // string & regular expression
  MatchCollection matchedAuthors = 
                  rgex.Matches(str);    

  // Print Yes If the string matches
  // with the Regex
  if (matchedAuthors.Count != 0)
    Console.WriteLine("Yes");
  else
    Console.WriteLine("No");
}

// Driver Code
public static void Main(String []args)
{
  // Given string str
  String str = "@#$&%!~";

  // Function Call
  onlySpecialchars(str);
}
}

// This code is contributed by Princi Singh

<script>

      // JavaScript program to check if
      // the string contains only
      // special characters
      
      // Function to check if a string
      // contains only special characters
      function onlySpecialchars(str) 
      {
        // Regex to check if a string
        // contains only special
        // characters
        var regex = /^[^a-zA-Z0-9]+$/;

        // If the string is empty
        // then print No
        if (str.length < 1) {
          document.write("No");
          return;
        }

        // Find match between given
        // string & regular expression
        var matchedAuthors = regex.test(str);

        // Print Yes If the string matches
        // with the Regex
        if (matchedAuthors) document.write("Yes");
        else document.write("No");
      }

      // Driver Code
     
     // Given string str
      var str = "@#$&%!~";
     
     // Function Call
      onlySpecialchars(str);
      
 </script>

Yes

Time Complexity: O(N)
Auxiliary Space: O(1)

Another approach: This is simple approach in which just checking the string contain any alphabets and digits or not. If contains then print No else print Yes.

1. Take the a string str and call the function Check_Special_Chars passing string as parameter.

2. The function Check_Special_Chars takes a string as input and loops over each character in the string using a for loop.

3. Now in the inner loop check each character is an alphabet (both upper and lower case)  A to Z  ASCII value (65 to 90) and a to z  ASCII value(97 to 122) or not. 

      If the character is an alphabet, the function prints "No" and returns from the function.

4.The second inner for loop checks if the current character is a number (0 to 9)  ASCII value(48 to 57). If the character is a number, the function prints "No" and returns from the function.

5. If the function loops through the entire string without finding any alphabets or numbers, it means that the string only contains special characters. In this case, the function prints "Yes".

Below the implementation of above approach.

// C++ program to check if the string
// contains only special characters
#include <bits/stdc++.h>
using namespace std;

// Function to check if the string contains only special characters.
void Check_Special_Chars(string s)
{
    // Looping over the string
  for(int i = 0; i<s.length();i++)
  {  
      // checking for a-z and A-Z characters
      for(int k = 0; k <26; k++)
      {
          // if present then print No and return
          if(s[i]==k+65 || s[i]==k+97)  
          {
              cout<<"No"<<endl;
              return;
          }
      }
      // Checking for 0-9 characters
      for(int k = 0; k<10; k++)
      {
           // if present then print No and return
          if(s[i]==k+48)
          {
              cout<<"No"<<endl;
              return;
          }
      }
  }
  // if not present a-z, A-Z and 0-9, then only special character present and print Yes
  cout<<"Yes"<<endl;
}

// Driver Code
int main()
{
// Given string str
string str = "@#$&%!~";
Check_Special_Chars(str) ;
return 0;
}

import java.util.*;

class Main {
    
    // Function to check if the string contains only special characters.
    static void Check_Special_Chars(String s) {
        // Looping over the string
        for(int i = 0; i < s.length(); i++) {
            // checking for a-z and A-Z characters
            for(int k = 0; k < 26; k++) {
                // if present then print No and return
                if(s.charAt(i) == (char)(k + 65) || s.charAt(i) == (char)(k + 97)) {
                    System.out.println("No");
                    return;
                }
            }
            // Checking for 0-9 characters
            for(int k = 0; k < 10; k++) {
                // if present then print No and return
                if(s.charAt(i) == (char)(k + 48)) {
                    System.out.println("No");
                    return;
                }
            }
        }
        // if not present a-z, A-Z and 0-9, then only special character present and print Yes
        System.out.println("Yes");
    }
    
    // Driver Code
    public static void main(String[] args) {
        // Given string str
        String str = "@#$&%!~";
        Check_Special_Chars(str);
    }
}

class Main:
    # Function to check if the string contains only special characters.
    @staticmethod
    def Check_Special_Chars(s):
        # Looping over the string
        for i in range(len(s)):
            # checking for a-z and A-Z characters
            for k in range(26):
                # if present then print No and return
                if s[i] == chr(k + 65) or s[i] == chr(k + 97):
                    print("No")
                    return
            # Checking for 0-9 characters
            for k in range(10):
                # if present then print No and return
                if s[i] == chr(k + 48):
                    print("No")
                    return
        # if not present a-z, A-Z and 0-9, then only special character 
        # present and print Yes
        print("Yes")
    
    # Driver Code

        # Given string str
str = "@#$&%!~"
Main.Check_Special_Chars(str)

using System;

class Program 
{
  
    // Function to check if the string contains only special
    // characters.
    static void Check_Special_Chars(string s)
    {
      
        // Looping over the string
        for (int i = 0; i < s.Length; i++) 
        {
          
            // checking for a-z and A-Z characters
            for (int k = 0; k < 26; k++) 
            {
              
                // if present then print No and return
                if (s[i] == k + 65 || s[i] == k + 97) {
                    Console.WriteLine("No");
                    return;
                }
            }
            // Checking for 0-9 characters
            for (int k = 0; k < 10; k++)
            {
              
                // if present then print No and return
                if (s[i] == k + 48) {
                    Console.WriteLine("No");
                    return;
                }
            }
        }
      
        // if not present a-z, A-Z and 0-9, then only
        // special character present and print Yes
        Console.WriteLine("Yes");
    }

    // Driver Code
    static void Main(string[] args)
    {
        // Given string str
        string str = "@#$&%!~";
        Check_Special_Chars(str);
    }
}

// Function to check if the string contains only special characters.
function Check_Special_Chars(s) {
  // Looping over the string
  for (let i = 0; i < s.length; i++) {
    // checking for a-z and A-Z characters
    for (let k = 0; k < 26; k++) {
      // if present then print No and return
      if (s[i] == String.fromCharCode(k + 65) || s[i] == String.fromCharCode(k + 97)) {
        console.log("No");
        return;
      }
    }
    // Checking for 0-9 characters
    for (let k = 0; k < 10; k++) {
      // if present then print No and return
      if (s[i] == String.fromCharCode(k + 48)) {
        console.log("No");
        return;
      }
    }
  }
  // if not present a-z, A-Z and 0-9, then only special character present and print Yes
  console.log("Yes");
}

// Driver Code
let str = "@#$&%!~";
Check_Special_Chars(str);

Yes

Time Complexity: O(N)
Auxiliary Space: O(1)