Encryption and Decryption of String according to given technique

Given a string S, the task is to encrypt the string and decrypt the string again to the original form. 
Encryption Technique: If L is the length of the string, then take two values, one the ceil of ?L (say b), and the other floor of ?L (say a), and make a two-dimensional matrix having rows = a, and columns = b. 
If rows*columns < L, then increase the value of a or b, whichever is minimum. Fill the matrix with the characters of the original string sequentially. After obtaining the matrix, read the matrix column-wise and print the obtained string. 
 

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Decryption Technique: If L is the length of the encrypted string, then again find the two values a and b, where a is the ceil value of the ?L and b is the floor value of the ?L. Similarly create a 2D Matrix in which store the string column-wise and read the matrix row-wise to get the string in the original form. 
 

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Encryption Approach: 
 

• Find the length L of the string.
• Find the ceil and floor values of ?Length and assign them to the variables.
• Check if the product of the two variables >= Length, if not then increments the variable having a lesser value by 1.
• Create a 2D matrix and fill the characters of the string row-wise.
• Read the matrix column-wise to get the encrypted string.

Decryption Approach: 
 

• Find the length L of the string.
• Find the ceil and floor values of ?Length and assign them to the variables.
• Create a 2D matrix and fill the matrix by characters of string column-wise.
• Read the matrix row-wise to get the decrypted string.

Below is the implementation of the above approach:
 

Gsree keFGskoe 
Geeks For Geeks

Time Complexity: O(?n * ?n) ? O(n)
Auxiliary Space: O(n), where n is the length of the given string.