Thousand Separator
<p>Given an integer <code>n</code>, add a dot (&quot;.&quot;) as the thousands separator and return it in string format.</p>

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

<pre>
<strong>Input:</strong> n = 987
<strong>Output:</strong> &quot;987&quot;
</pre>

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

<pre>
<strong>Input:</strong> n = 1234
<strong>Output:</strong> &quot;1.234&quot;
</pre>

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

<ul>
	<li><code>0 &lt;= n &lt;= 2<sup>31</sup> - 1</code></li>
</ul>
String
class Solution {
public:
    string thousandSeparator(int n) {
        int cnt = 0;
        string ans;
        while (1) {
            int v = n % 10;
            n /= 10;
            ans += to_string(v);
            if (n == 0) break;
            if (++cnt == 3) {
                ans += '.';
                cnt = 0;
            }
        }
        reverse(ans.begin(), ans.end());
        return ans;
    }
};