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Decrypt a string encrypted by repeating i-th character i times
• Last Updated : 27 May, 2021

Given an encrypted string str and the encryption algorithm, the task is to decrypt the string. The encryption algorithm is as follows:
The 1st character of the string will be repeated once in the encrypted string, the 2nd character will be repeated twice, …, nth character will be repeated n times. For example, the string “abcd” will be encrypted as “abbcccdddd”.

Examples:

Input: str = “geeeeekkkksssss”
Output: geeks

Input: str = “abbcccdddd”
Output: abcd

Approach: Initialize i = 0 and print str[i]
Update i = i + 1 and print str[i], then update i = i + 2 and print str[i] and so on while i < length(str).

Below is the implementation of the above approach:

## C++

 `// C++ implementation of the approach``#include ``using` `namespace` `std;` `// Function to return the decrypted string``string decryptString(string str, ``int` `n)``{` `    ``// Initial jump will be 1``    ``int` `i = 0, jump = 1;``    ``string decryptedStr = ``""``;` `    ``while` `(i < n) {``        ``decryptedStr += str[i];``        ``i += jump;` `        ``// Increment jump by 1 with every character``        ``jump++;``    ``}` `    ``return` `decryptedStr;``}` `// Driver code``int` `main()``{``    ``string str = ``"geeeeekkkksssss"``;``    ``int` `n = str.length();``    ``cout << decryptString(str, n);` `    ``return` `0;``}`

## Java

 `// Java implementation of the approach``class` `GFG``{` `// Function to return the decrypted string``static` `String decryptString(String str, ``int` `n)``{` `    ``// Initial jump will be 1``    ``int` `i = ``0``, jump = ``1``;``    ``String decryptedStr = ``""``;` `    ``while` `(i < n)``    ``{``        ``decryptedStr += str.charAt(i);``        ``i += jump;` `        ``// Increment jump by 1 with every character``        ``jump++;``    ``}` `    ``return` `decryptedStr;``}` `// Driver code``public` `static` `void` `main(String[] args)``{``    ``String str = ``"geeeeekkkksssss"``;``    ``int` `n = str.length();``    ``System.out.println(decryptString(str, n));``}``}` `// This code is contributed by Code_Mech`

## Python3

 `# Python 3 implementation of the approach` `# Function to return the decrypted string``def` `decryptString(``str``, n):``    ` `    ``# Initial jump will be 1``    ``i ``=` `0``    ``jump ``=` `1``    ``decryptedStr ``=` `""` `    ``while` `(i < n):``        ``decryptedStr ``+``=` `str``[i];``        ``i ``+``=` `jump` `        ``# Increment jump by 1 with``        ``# every character``        ``jump ``+``=` `1` `    ``return` `decryptedStr` `# Driver code``if` `__name__ ``=``=` `'__main__'``:``    ``str` `=` `"geeeeekkkksssss"``    ``n ``=` `len``(``str``)``    ``print``(decryptString(``str``, n))` `# This code is contributed by``# Surendra_Gangwar`

## C#

 `// C# implementation of the approach``using` `System;` `class` `GFG``{` `// Function to return the decrypted string``static` `string` `decryptString(``string` `str, ``int` `n)``{` `    ``// Initial jump will be 1``    ``int` `i = 0, jump = 1;``    ``string` `decryptedStr = ``""``;` `    ``while` `(i < n)``    ``{``        ``decryptedStr += str[i];``        ``i += jump;` `        ``// Increment jump by 1 with every character``        ``jump++;``    ``}` `    ``return` `decryptedStr;``}` `// Driver code``public` `static` `void` `Main()``{``    ``string` `str = ``"geeeeekkkksssss"``;``    ``int` `n = str.Length;``    ``Console.Write(decryptString(str, n));``}``}` `// This code is contributed by ita_c`

## PHP

 ``

## Javascript

 ``
Output:
`geeks`

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