<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, int numRows) {

        if (numRows == 1) {
            return s;
        }

        vector<string> strcols;

        int cnt = 0, row = 0, col = 0;
        bool flag = true;
        string sub;
        for (size_t idx = 0; idx < s.size(); idx++) {

            if (flag) {
                sub += s[idx];
                if (row == numRows - 1 || idx == s.size()  - 1) {
                    col ++;
                    cout << sub << endl;
                    strcols.push_back(sub);

                    flag = false;
                    row--;
                    if (row == 0) {
                        flag = true;
                        sub.clear();
                    }
                }
                else {
                    row++;
                }
            }
            else {
                sub = string(numRows, ' ');
                sub[row] = s[idx];
                cout << sub << endl;
                strcols.push_back(sub);

                row--;
                col++;

                if (row <= 0) {
                    row = 0;
                    flag = true;
                    sub.clear();
                }
            }
        }

        string output;
        for (int row = 0; row < numRows; row++) {
            for (int col = 0; col < strcols.size(); col++) {
                if (row < strcols[col].size()) {
                    if (strcols[col][row] != ' ') {
                        output += strcols[col][row];
                    }
                }
            }
        }

        return output;
    }
};
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