Integer to Roman
<p>Seven different symbols represent Roman numerals with the following values:</p>

<table>
	<thead>
		<tr>
			<th>Symbol</th>
			<th>Value</th>
		</tr>
	</thead>
	<tbody>
		<tr>
			<td>I</td>
			<td>1</td>
		</tr>
		<tr>
			<td>V</td>
			<td>5</td>
		</tr>
		<tr>
			<td>X</td>
			<td>10</td>
		</tr>
		<tr>
			<td>L</td>
			<td>50</td>
		</tr>
		<tr>
			<td>C</td>
			<td>100</td>
		</tr>
		<tr>
			<td>D</td>
			<td>500</td>
		</tr>
		<tr>
			<td>M</td>
			<td>1000</td>
		</tr>
	</tbody>
</table>

<p>Roman numerals are formed by appending&nbsp;the conversions of&nbsp;decimal place values&nbsp;from highest to lowest. Converting a decimal place value into a Roman numeral has the following rules:</p>

<ul>
	<li>If the value does not start with 4 or&nbsp;9, select the symbol of the maximal value that can be subtracted from the input, append that symbol to the result, subtract its value, and convert the remainder to a Roman numeral.</li>
	<li>If the value starts with 4 or 9 use the&nbsp;<strong>subtractive form</strong>&nbsp;representing&nbsp;one symbol subtracted from the following symbol, for example,&nbsp;4 is 1 (<code>I</code>) less than 5 (<code>V</code>): <code>IV</code>&nbsp;and 9 is 1 (<code>I</code>) less than 10 (<code>X</code>): <code>IX</code>.&nbsp;Only the following subtractive forms are used: 4 (<code>IV</code>), 9 (<code>IX</code>),&nbsp;40 (<code>XL</code>), 90 (<code>XC</code>), 400 (<code>CD</code>) and 900 (<code>CM</code>).</li>
	<li>Only powers of 10 (<code>I</code>, <code>X</code>, <code>C</code>, <code>M</code>) can be appended consecutively at most 3 times to represent multiples of 10. You cannot append 5&nbsp;(<code>V</code>), 50 (<code>L</code>), or 500 (<code>D</code>) multiple times. If you need to append a symbol&nbsp;4 times&nbsp;use the <strong>subtractive form</strong>.</li>
</ul>

<p>Given an integer, convert it to a Roman numeral.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">num = 3749</span></p>

<p><strong>Output:</strong> <span class="example-io">&quot;MMMDCCXLIX&quot;</span></p>

<p><strong>Explanation:</strong></p>

<pre>
3000 = MMM as 1000 (M) + 1000 (M) + 1000 (M)
 700 = DCC as 500 (D) + 100 (C) + 100 (C)
  40 = XL as 10 (X) less of 50 (L)
   9 = IX as 1 (I) less of 10 (X)
Note: 49 is not 1 (I) less of 50 (L) because the conversion is based on decimal places
</pre>
</div>

<p><strong class="example">Example 2:</strong></p>

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">num = 58</span></p>

<p><strong>Output:</strong> <span class="example-io">&quot;LVIII&quot;</span></p>

<p><strong>Explanation:</strong></p>

<pre>
50 = L
 8 = VIII
</pre>
</div>

<p><strong class="example">Example 3:</strong></p>

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">num = 1994</span></p>

<p><strong>Output:</strong> <span class="example-io">&quot;MCMXCIV&quot;</span></p>

<p><strong>Explanation:</strong></p>

<pre>
1000 = M
 900 = CM
  90 = XC
   4 = IV
</pre>
</div>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= num &lt;= 3999</code></li>
</ul>
Hash Table; Math; String
class Solution {
    /**
     * @param Integer $num
     * @return String
     */
    function intToRoman($num) {
        $cs = ['M', 'CM', 'D', 'CD', 'C', 'XC', 'L', 'XL', 'X', 'IX', 'V', 'IV', 'I'];
        $vs = [1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1];
        $ans = '';

        foreach ($vs as $i => $v) {
            while ($num >= $v) {
                $num -= $v;
                $ans .= $cs[$i];
            }
        }

        return $ans;
    }
}