ZigZag conversion

Problem Statement

Given a string, write it in a zigzag pattern on a given number of rows and then read the result line by line.

For example, the string "PAYPALISHIRING" written in a zigzag pattern with 3 rows looks like:

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

Reading line by line gives: "PAHNAPLSIIGYIR".

Implement the following function:

def convert(s: str, numRows: int) -> str:

Examples

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 Template

class Solution:
    def convert(self, s: str, numRows: int) -> str:
        # Write your code here
        pass

Solutions

• Solution 1: This solution uses a list of strings to represent each row and simulates the zigzag pattern by iterating through the characters of the input string. It has a time complexity of O(n) and a space complexity of O(n).
• Solution 2: This solution calculates the positions of characters in each row directly based on the zigzag pattern, avoiding the need for direction tracking. It also has a time complexity of O(n) and a space complexity of O(1).

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