<p>The string <code>&quot;PAYPALISHIRING&quot;</code> 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>

<pre>
P   A   H   N
A P L S I I G
Y   I   R
</pre>

<p>And then read line by line: <code>&quot;PAHNAPLSIIGYIR&quot;</code></p>

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

<pre>
string convert(string s, int numRows);
</pre>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;PAYPALISHIRING&quot;, numRows = 3
<strong>Output:</strong> &quot;PAHNAPLSIIGYIR&quot;
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;PAYPALISHIRING&quot;, numRows = 4
<strong>Output:</strong> &quot;PINALSIGYAHRPI&quot;
<strong>Explanation:</strong>
P     I    N
A   L S  I G
Y A   H R
P     I
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;A&quot;, numRows = 1
<strong>Output:</strong> &quot;A&quot;
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= s.length &lt;= 1000</code></li>
	<li><code>s</code> consists of English letters (lower-case and upper-case), <code>&#39;,&#39;</code> and <code>&#39;.&#39;</code>.</li>
	<li><code>1 &lt;= numRows &lt;= 1000</code></li>
</ul>

class Solution:
    def convert(self, s: str, numRows: int) -> str:
        group_s = []
        if numRows > 1:
            group_len = numRows*2 - 2
        else:
            group_len = 1
        
        group_len_all = len(s)
        group_cnt = group_len_all // group_len 
        for i in range(group_cnt + 1):
            # add first numRows elements as first array
            group_string = s[i * group_len: (i+1) * group_len]
            group_string_len = len(group_string)

            if group_string_len >= numRows:
                group_s.append(list(group_string[:numRows]))

                # add other arrays in this group
                
                for j in range(group_string_len - numRows):
                    group_s_elem = [''] * numRows
                    group_s_elem_loc = numRows - j - 2
                    group_s_elem[group_s_elem_loc] = group_string[numRows + j]
                    group_s.append(group_s_elem)

            elif group_string_len < numRows:
                group_s.append(list(group_string ) + [''] * (numRows - group_string_len))

        ret = []
        for m in range(numRows):
            for n in range(len(group_s)):
                ret.append(group_s[n][m])

        return "".join(ret)
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