Decode the Slanted Ciphertext — LeetCode 2075 Python Solution

The problem

A string originalText is encoded using a slanted transposition cipher to a string encodedText with the help of a matrix having a fixed number of rows rows. originalText is placed first in a top-left to bottom-right manner.

Example

Input

encodedText = "ch ie pr", rows = 3

Output

"cipher"

Explanation

This is the same example described in the problem description.

Python solution

class Solution:
    def decodeCiphertext(self, encodedText: str, rows: int) -> str:
        ans = []
        cols = len(encodedText) // rows
        for j in range(cols):
            x, y = 0, j
            while x < rows and y < cols:
                ans.append(encodedText[x * cols + y])
                x, y = x + 1, y + 1
        return ''.join(ans).rstrip()

Complexity

Pattern: Hash Map

Trade memory for time: remember what you have seen so the second pass never happens. LeetCode 2075. Decode the Slanted Ciphertext is filed here because the reference solution below belongs to the algorithm family this hub collects, even though its LeetCode tags point elsewhere.

The hash map guide has the Python template for the pattern and the 709 LeetCode problems that use it.

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