<p>To match 3 digit patterns, we can use <code>[0-9][0-9][0-9]</code>. What if we have n digit patterns? We have to write <code>[0-9]</code> n times, but that is a waste of time. Here is when quantifiers come for help.</p>
<ol>
<li><p><strong>Limiting repetitions(<code>{min, max}</code>):</strong> To match n digit patterns, we can simply write <code>[0-9]{n}</code>. Instead of n, by providing minimum and maximum values as-<code>[0-9]{min, max}</code>, we can match a pattern repeating min to max times.</p>
<p>Let's see an example to match all numbers between 1 to 999.</p>
<p><strong>Note:</strong> If you don't write the upper bound(<code>{min,}</code>), then it basically means, there is no limit for maximum repetitions.</p>
<li><strong><code>?</code> quantifier:</strong> It is equivalent to <code>{0,1}</code>, either zero or one occurrence. <code>?</code> is very useful for optional occurrences in patterns.</li>
<p><strong>Now, you may be thinking, what if we want to match characters like <code>*, ?, +, {, }</code> in the text, they are special characters. Check it out in the appendix.</strong></p>
<h3id="problems">Problems</h3>
<ol>
<li><p>Find out a regex to match positive integers or floating point numbers with exactly two characters after the decimal point.</p>
<p>HTML tag is represented as <code><tag_name>some text</tag_name></code>. For example, <code><title>Regular expression</title></code></p>
<p>So, rather than matching up till first <code>></code>, it matches the whole tag. So, quantifiers are greedy by default. It is called <strong>Greediness!</strong>.</p>
<p>To solve this issue, we use <code>?</code> quantifier and it is called <strong>lazy matching</strong>. We will discuss it next.</p>
