<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:
int noofclm(string s, int numRows) {
        if (numRows == 1) return s.size();
        int n = s.size();
        int clm = 0;
        bool flag = true;
        while (n > 0) {
            if (flag) {
                clm++;
                n -= numRows;
                flag = false;
            } else {
                clm += (numRows - 2);
                n -= (numRows - 2);
                flag = true;
            }
        }
        return clm;
    }
    
    string convert(string s, int numRows) {
        if (numRows == 1) {
            return s;
        }
        int clm = noofclm(s, numRows);
        vector<vector<char>> zigzag(numRows, vector<char>(clm, ' ')); 
        int i = 0;
        int col = 0;
        while (i < s.size()) {
            for (int row = 0; row < numRows && i < s.size(); row++) {
                zigzag[row][col] = s[i++];
            }
            for (int row = numRows - 2; row >= 1 && i < s.size(); row--) {
                zigzag[row][++col] = s[i++];
            }
            col++;
        }
        
        string str = "";
        for (int i = 0; i < numRows; i++) {
            for (int j = 0; j < clm; j++) {
                if (zigzag[i][j] != ' ') {
                    str += zigzag[i][j];
                }
            }
        }
        return str;
    }
};
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