# Encrypt a string by repeating i-th character i times

• Last Updated : 08 Aug, 2022

Given string str, the task is to encrypt the string with the given encryption algorithm. The 1st character of the string will be repeated once in the encrypted string, the 2nd character will be repeated twice, â€¦, nth character will be repeated n times.

Examples:

```Input: str = "geeks"
Output: geeeeekkkksssss

Input: str = "abcd"
Output: abbcccdddd   ```

Approach: Initialize cnt = 1 and start traversing the string character by character. Repeat the current character cnt number of times then update cnt = cnt + 1 and get to the next character. Repeat these steps for every character of the string.

Below is the implementation of the above approach:

## C++

 `// C++ implementation of the approach``#include ``using` `namespace` `std;` `// Function to return the encrypted string``string encryptString(string str, ``int` `n)``{``    ``int` `i = 0, cnt = 0;``    ``string encryptedStr = ``""``;` `    ``while` `(i < n) {` `        ``// Number of times the current``        ``// character will be repeated``        ``cnt = i + 1;` `        ``// Repeat the current character``        ``// in the encrypted string``        ``while` `(cnt--)``            ``encryptedStr += str[i];``        ``i++;``    ``}` `    ``return` `encryptedStr;``}` `// Driver code``int` `main()``{``    ``string str = ``"geeks"``;``    ``int` `n = str.length();``    ``cout << encryptString(str, n);` `    ``return` `0;``}`

## Java

 `// Java implementation of the approach``class` `GFG``{` `// Function to return the encrypted String``static` `String encryptString(String str, ``int` `n)``{``    ``int` `i = ``0``, cnt = ``0``;``    ``String encryptedStr = ``""``;` `    ``while` `(i < n)``    ``{` `        ``// Number of times the current``        ``// character will be repeated``        ``cnt = i + ``1``;` `        ``// Repeat the current character``        ``// in the encrypted String``        ``while` `(cnt-- >``0``)``            ``encryptedStr += str.charAt(i);``        ``i++;``    ``}` `    ``return` `encryptedStr;``}` `// Driver code``public` `static` `void` `main(String[] args)``{``    ``String str = ``"geeks"``;``    ``int` `n = str.length();``    ``System.out.println(encryptString(str, n));``}``}` `// This code has been contributed by 29AjayKumar`

## Python3

 `# Python3 implementation of the approach` `# Function to return the encrypted string``def` `encryptString(string, n):` `    ``i, cnt ``=` `0``, ``0``    ``encryptedStr ``=` `""` `    ``while` `i < n:` `        ``# Number of times the current``        ``# character will be repeated``        ``cnt ``=` `i ``+` `1` `        ``# Repeat the current character``        ``# in the encrypted string``        ``while` `cnt > ``0``:``            ``encryptedStr ``+``=` `string[i]``            ``cnt ``-``=` `1``            ` `        ``i ``+``=` `1` `    ``return` `encryptedStr` `# Driver code``if` `__name__ ``=``=` `"__main__"``:` `    ``string ``=` `"geeks"``    ``n ``=` `len``(string)``    ``print``(encryptString(string, n))` `# This code is contributed``# by Rituraj Jain`

## C#

 `// C# implementation of the approach``using` `System;` `class` `GFG``{``    ` `// Function to return the encrypted String``static` `String encryptString(String str, ``int` `n)``{``    ``int` `i = 0, cnt = 0;``    ``String encryptedStr = ``""``;` `    ``while` `(i < n)``    ``{` `        ``// Number of times the current``        ``// character will be repeated``        ``cnt = i + 1;` `        ``// Repeat the current character``        ``// in the encrypted String``        ``while` `(cnt-- >0)``            ``encryptedStr += str[i];``        ``i++;``    ``}` `    ``return` `encryptedStr;``}` `// Driver code``static` `public` `void` `Main ()``{``    ``String str = ``"geeks"``;``    ``int` `n = str.Length;``    ``Console.WriteLine(encryptString(str, n));``}``}` `// This code is contributed by ajit`

## PHP

 ``

## Javascript

 ``

Output:

`geeeeekkkksssss`

Time Complexity: O(n) // n is the length of the string

Auxiliary Space: O(1)

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