<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:
    void diagonal(string s, vector<vector<char>>& store, int &i, int &j, int& ind, int n){
        while(i >= 0 && ind < s.size()) store[i--][j++] = s[ind++];
        --j;
        i = 1;
    }
    void vertical(string s, vector<vector<char>>& store, int &i, int &j, int& ind, int rows, int n){
        while(i < rows - 1 && ind < s.size()) store[i++][j] = s[ind++];
    }
    string convert(string s, int rows) {
        int n = s.size(), ind = 0, i = 0, j = 0;
        if(rows == 1 || n == 1) return s;
        vector<vector<char>> store(rows + 1, vector<char>(n / 2 + 1, ' '));
        while(ind < n){
            vertical(s, store, i, j, ind, rows, n);
            diagonal(s, store, i, j, ind, n);
        }
        string ans = "";
        for(int i = 0; i < store.size(); i++){
            for(int j = 0; j < store[0].size(); j++){
                if(store[i][j] != ' ') ans.push_back(store[i][j]);
            }
        }
        return ans;
    }
};
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