Add index to characters and reverse the string Last Updated : 07 Aug, 2022 Comments Improve Suggest changes Like Article Like Report Given a string str, the task is to encrypt and reverse the string. The string is encrypted by adding every character of the string with it's index in the string i.e. if character'a' is at index 2 then the character in the updated string will be 'a' + 2 = 'c'. Since value of string may go beyond 256, do the addition under modulo 256.Examples: Input: str = "geeks" Output: wngfg 'g' + 0 = 'g' 'e' + 1 = 'f' 'e' + 2 = 'g' 'k' + 3 = 'n' 's' + 4 = 'w' Input: str = "java" Output: dxbj Approach: Add every character of the string with its index within the same string.Reverse the string.Print the reversed string. Below is the implementation of the above approach: C++ // C++ implementation of the approach #include <bits/stdc++.h> using namespace std; // Function to return the encryptet string string getEncryptedString(string str) { // To build the encrypted string string sb =""; // Traverse the string in reverse for (int i = str.length() - 1; i >= 0; i--) { sb+=(char)((int)str[i] + i) % 256; } // Return the encrypted string return sb; } // Driver code int main() { string str = "geeks"; cout<<getEncryptedString(str)<<endl; return 0; } // This code is contributed by mits Java // Java implementation of the approach public class HelloWorld { // Function to return the encryptet string static String getEncryptedString(String str) { // To build the encrypted string StringBuilder sb = new StringBuilder(""); // Traverse the string in reverse for (int i = str.length() - 1; i >= 0; i--) { sb.append("" + (char)((str.charAt(i) + i) % 256)); } // Return the encrypted string return sb.toString(); } // Driver code public static void main(String[] args) { String str = "geeks"; System.out.println(getEncryptedString(str)); } } Python3 # Python3 implementation of the approach # Function to return the encryptet string def getEncryptedString(str): # To build the encrypted string sb = ""; # Traverse the string in reverse for i in range(len(str) - 1,-1,-1): sb += chr((ord(str[i]) + i) % 256); # Return the encrypted string return sb; # Driver code str = "geeks"; print(getEncryptedString(str)); # This code is contributed by mits C# // C# implementation of the approach using System; using System.Text; public class HelloWorld { // Function to return the encryptet string static String getEncryptedString(String str) { // To build the encrypted string StringBuilder sb = new StringBuilder(""); // Traverse the string in reverse for (int i = str.Length - 1; i >= 0; i--) { sb.Append("" + (char)((str[i] + i) % 256)); } // Return the encrypted string return sb.ToString(); } // Driver code public static void Main(String[] args) { String str = "geeks"; Console.WriteLine(getEncryptedString(str)); } } // This code contributed by Rajput-Ji PHP <?php // PHP implementation of the approach // Function to return the encryptet string function getEncryptedString($str) { // To build the encrypted string $sb = ""; // Traverse the string in reverse for ($i = strlen($str) - 1; $i >= 0; $i--) { $sb .= chr((ord($str[$i]) + $i) % 256); } // Return the encrypted string return $sb; } // Driver code $str = "geeks"; print(getEncryptedString($str)); // This code is contributed by mits ?> JavaScript <script> // javascript implementation of the approach // Function to return the encryptet string function getEncryptedString( str) { // To build the encrypted string sb = ""; // Traverse the string in reverse for (i = str.length - 1; i >= 0; i--) { sb+=("" + String.fromCharCode((str.charCodeAt(i) + i) % 256)); } // Return the encrypted string return sb; } // Driver code var str = "geeks"; document.write(getEncryptedString(str)); // This code is contributed by Rajput-Ji </script> Output: wngfg Time complexity: O(N) where N is length of given string Auxiliary Space: O(1) Comment More infoAdvertise with us Next Article Add index to characters and reverse the string A Abhishek_Ranjan Follow Improve Article Tags : DSA Technical Scripter 2018 Reverse Practice Tags : Reverse Similar Reads Reverse a string without affecting special characters Given a string, that contains a special character together with alphabets ('a' to 'z' and 'A' to 'Z'), reverse the string in a way that special characters are not affected. 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