换位密码(Transposition Cipher)返回错误结果，请求代码故障排查

Hey there! Let's figure out why your transposition cipher code is returning that jumbled string instead of the expected "Common sence is not so common." Transposition ciphers live or die by how correctly they rearrange characters, so the problem is almost certainly in the rearrangement logic. Here are the most likely issues to check:

1. Incorrect Column/Row Calculation #

Transposition ciphers rely on arranging text into a grid of rows and columns. If your code miscalculates either value, the character order will get completely messed up:

• Double-check how you're calculating rows: For encryption, rows should be the ceiling of len(plaintext) / key (you can compute this as (len(plaintext) + key - 1) // key in Python to avoid floating points).
• Make sure you're not swapping rows and columns by accident—this is a super common mix-up that leads to garbled output.

2. Mixed-Up Encryption/Decryption Flow #

It's easy to flip the logic between encrypting and decrypting:

• Encryption typically involves writing plaintext into the grid row-by-row, then reading it column-by-column to get ciphertext.
• Decryption does the reverse: write ciphertext column-by-column into the grid, then read row-by-row to get plaintext.
  If your code uses the encryption flow when it should be decrypting (or vice versa), you'll get exactly the kind of jumbled result you're seeing.

3. Botched Padding Handling #

When your input text length isn't a perfect multiple of the key, you need to add padding characters (like spaces) to fill out the grid. Issues here cause character misalignment:

• Check if your encryption code adds enough padding to make the total text length divisible by the key.
• Ensure your decryption code correctly removes those padding characters at the end—leaving them in or removing too many will throw off the final string.

4. Off-by-One Index Mistakes #

Python uses 0-based indexing, and even a tiny error here can break everything:

• For example, if you're calculating grid positions with row = i / key instead of row = i // key (integer division), or adding an extra +1 to column indices, you'll place characters in the wrong spots.
• Walk through a small example manually (like encrypting "Hello" with key 2) to see if your code's index calculations match what you'd do by hand.

5. Wrong Key or Input #

Don't overlook the basics:

• Are you using the exact same key that the example expects? A different key will rearrange characters in a completely different pattern.
• Double-check that your input text matches the example exactly—extra spaces, typos, or missing characters will throw off the result.

If you can share a snippet of your code, I can help pinpoint the exact line causing the issue!

内容的提问来源于stack exchange，提问作者Saix