<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 {
public:
    string convert(string s, short numRows) {
        if (numRows == 1) return s; // Edge case for single row
        
        map<short, list<char>> noteit;
        int k = 1;   // current row index
        int down = 1;  // direction flag
        int i = 0;
        int n = s.size();
        
        while (i < n) {
            noteit[k].push_back(s[i++]);
            
            // Change direction when reaching the first or last row
            if (k == numRows) {
                down = -1;
            } else if (k == 1) {
                down = 1;
            }

            // Move the index up or down based on the current direction
            if (down == 1) {
                k++;
            } else {
                k--;
            }
        }
        
        // Now build the result string
        string result;
        for (int j = 1; j <= numRows; j++) {
            while (!noteit[j].empty()) {
                result += noteit[j].front();
                noteit[j].pop_front();
            }
        }
        
        return result;
    }
};




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