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Zigzag Conversion

Problem Statement​

The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)

P   A   H   N
A P L S I I G
Y   I   R

And then read line by line: "PAHNAPLSIIGYIR"

Write the code that will take a string and make this conversion given a number of rows:

string convert(string s, int numRows);

Leetcode Link

Example 1:​

Input: s = "PAYPALISHIRING", numRows = 3
Output: "PAHNAPLSIIGYIR"

Example 2:​

Input: s = "PAYPALISHIRING", numRows = 4
Output: "PINALSIGYAHRPI"
Explanation:
P     I    N
A   L S  I G
Y A   H R
P     I

Example 3:​

Input: s = "A", numRows = 1
Output: "A"

Constraints:​

  • 1 <= s.length <= 1000
  • s consists of English letters (lower-case and upper-case), ',' and '.'.
  • 1 <= numRows <= 1000

Code​

Python Code
class Solution:
    def convert(self, s: str, numRows: int) -> str:
        template = list(range(numRows)) + list(range(numRows - 2, 0, -1))

        result = [''] * numRows
        for i, char in enumerate(s):
            result[template[i % len(template)]] += char
        return ''.join(result)