Related Articles

# Check if a string consists only of special characters

• Last Updated : 11 May, 2021

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++

 `// C++ program to check if the string``// contains only special characters``#include ``#include ``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 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

 `// 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);``    ``}``}`

## Python3

 `# 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#

 `// 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`

## Javascript

 ``
Output:
`Yes`

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

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.  To complete your preparation from learning a language to DS Algo and many more,  please refer Complete Interview Preparation Course.

In case you wish to attend live classes with experts, please refer DSA Live Classes for Working Professionals and Competitive Programming Live for Students.

My Personal Notes arrow_drop_up