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Caesar Cipher Encryption and Decryption

Certification: Intermediate Level Accuracy: 100% Submissions: 1 Points: 10

Write a Python program to implement Caesar Cipher encryption and decryption. Caesar Cipher is a substitution cipher where each letter in the plaintext is shifted a certain number of places down or up the alphabet. For example, with a shift of 3, A would be encoded as D, B would become E, and so on.

Example 1
    
  
  • Input: text = "HELLO", shift = 3
    • 
  
  • Output: "KHOOR"
    • 
  
  • Explanation: 
    • Each letter is shifted 3 positions forward in the alphabet. 
    • H becomes K, E becomes H, L becomes O, L becomes O, O becomes R. 
    • Therefore, "HELLO" becomes "KHOOR".
    •
Example 2
    
  
  • Input: text = "KHOOR", shift = -3
    • 
  
  • Output: "HELLO"
    • 
  
  • Explanation: 
    • Each letter is shifted 3 positions backward in the alphabet. 
    • K becomes H, H becomes E, O becomes L, O becomes L, R becomes O. 
    • Therefore, "KHOOR" becomes "HELLO" (decryption).
    •
Constraints
    
  
  • 1 ≤ text.length ≤ 1000
    • 
  
  • text consists of uppercase and lowercase English letters and spaces
    • 
  
  • -25 ≤ shift ≤ 25
    • 
  
  • Preserve the case of letters and keep spaces unchanged
    • 
  
  • Time Complexity: O(n)
    • 
  
  • Space Complexity: O(n)
    •
StringsFunctions / MethodsAccentureSwiggy
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Hint
Solution

Solution Hints

    
  
  • Iterate through each character in the input text
    • 
  
  • Check if the character is a letter (uppercase or lowercase)
    • 
  
  • Calculate the shifted position using modular arithmetic
    • 
  
  • Handle wrap-around cases (Z to A, z to a)
    • 
  
  • Preserve spaces and special characters as they are
    • 
  
  • Maintain the original case of the letters
    •

Steps to solve by this approach:

 Step 1: Initialize an empty result string to store the transformed text.
 Step 2: Iterate through each character in the input text.
 Step 3: Check if the character is an uppercase letter (A-Z).
 Step 4: If uppercase, apply shift using modular arithmetic with base 65 (ASCII 'A').
 Step 5: Check if the character is a lowercase letter (a-z).
 Step 6: If lowercase, apply shift using modular arithmetic with base 97 (ASCII 'a').
 Step 7: If character is not a letter, keep it unchanged (spaces, punctuation).
 Step 8: Add the transformed character to the result string.

Submitted Code :