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Leetcode - ZigZag Conversion Solution

Poor Man
Published
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1 min read

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)

Text
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:

Text
string convert(string s, int numRows);

Example 1:

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

Example 2:

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

Example 3:

Text
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

Solution in Python#

Python
class Solution:
    def convert(self, s: str, numRows: int) -> str:
        d = defaultdict(str)
        r = 1
        x = 1
        for i in s:
            d[x]+=i
            x += r
            if x == numRows or x==1:
                r*=-1

        return "".join(d.values())

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