Decrypt a string encrypted by repeating i-th character i times

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, 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++

filter_none

edit
close

play_arrow

link
brightness_4
code

// C++ implementation of the approach
#include <bits/stdc++.h>
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;
}

chevron_right


Java

filter_none

edit
close

play_arrow

link
brightness_4
code

// 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

chevron_right


Python3

filter_none

edit
close

play_arrow

link
brightness_4
code

# 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

chevron_right


C#

filter_none

edit
close

play_arrow

link
brightness_4
code

// 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

chevron_right


PHP

filter_none

edit
close

play_arrow

link
brightness_4
code

<?php
// PHP implementation of the approach 
  
// Function to return the decrypted string 
function 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++; 
    }
    return $decryptedStr
  
// Driver code 
$str = "geeeeekkkksssss"
$n = strlen($str); 
echo decryptString($str, $n); 
  
// This code is contributed by Ryuga
?>

chevron_right


Output:

geeks


My Personal Notes arrow_drop_up

good platform for learning

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.





Article Tags :
Practice Tags :


Be the First to upvote.


Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.