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Encrypt a string by repeating i-th character i times

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  • Last Updated : 08 Aug, 2022
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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, …, 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 <bits/stdc++.h>
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




<?php
// PHP implementation of the approach
 
// Function to return the encrypted string
function encryptString($str, $n)
{
    $i = 0 ;
    $cnt = 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--)
            $encryptedStr .= $str[$i];
        $i++;
    }
 
    return $encryptedStr;
}
 
// Driver code
$str = "geeks";
$n = strlen($str);
 
echo encryptString($str, $n);
 
// This code is contributed by Ryuga
?>

Javascript




<script>
    // Javascript implementation of the approach
     
    // Function to return the encrypted String
    function encryptString(str, n)
    {
        let i = 0, cnt = 0;
        let 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;
    }
     
    let str = "geeks";
    let n = str.length;
    document.write(encryptString(str, n));
         
</script>

Output: 

geeeeekkkksssss

 

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

Auxiliary Space: O(1)


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