<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>

#include <string>
#include <vector>

class Solution {
public:
    void create(string s,vector<vector<char>>& v, int row, int col, int index) {
        if (index >= s.size()) {
            return;
        }
         if (row == 0   && index < s.size()) {
            while (row < v.size()-1 && index < s.size()) { 
                v[row][col] = s[index];
                row++;
                index++; 
            }
        }
        if (row == v.size() - 1  && index < s.size()) { 
            while (row > 0 && index < s.size()) {  
                v[row][col] = s[index];
                row--;
                col++;
                index++;
            }
        }
        create(s, v, row, col, index);  
    }

    std::string convert(std::string s, int numRows) {
        if (numRows == 1) return s;  // Special case for single row
        string output;
        int numCols =  (s.size() / (2 * numRows - 2) + 1) * (numRows - 1);
        vector<vector<char>> v(numRows,vector<char>(numCols, '\0'));
        create(s, v, 0, 0, 0);
        for (int i = 0; i < numRows; i++) {
            for (int j = 0; j < numCols; j++) {
                if (v[i][j] != '\0') {
                    output.push_back(v[i][j]);
                }
            }
        }
        return output;
    }
};

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