RAILFENCE DECRYPTION - PE

def rail_fence_decrypt(ciphertext, num_rails):
# Create a grid with empty placeholders
grid = [['' for _ in range(len(ciphertext))] for _ in range(num_rails)]

#Create the zigzag pattern on the grid
index, step = 0, 1
for i in range(len(ciphertext)):
    grid[index][i] = '*'
    if index == 0:
        step = 1
    elif index == num_rails - 1:
        step = -1
    index += step

#Fill the grid with ciphertext characters
idx = 0
for r in range(num_rails):
    for c in range(len(ciphertext)):
        if grid[r][c] == '*':
            grid[r][c] = ciphertext[idx]
            idx += 1

#Read the message from the grid in a zigzag pattern
decrypted_message = []
index, step = 0, 1
for i in range(len(ciphertext)):
    decrypted_message.append(grid[index][i])
    if index == 0:
        step = 1
    elif index == num_rails - 1:
        step = -1
    index += step

return ''.join(decrypted_message)

def main():
# Sample Ciphertext
ciphertext = "HOIEL REDLFN"
num_rails = 3

#Decrypting the message
decrypted = rail_fence_decrypt(ciphertext, num_rails)

#Display the results
print("\n--- Output ---")
print("Ciphertext:", ciphertext)
print("Decrypted (Rail Fence):", decrypted)

if name == "main":
main()