Greedy vs Lazy Matching

By default, quantifiers are greedy - they match as much as possible. Adding ? makes them lazy - matching as little as possible.

Greedy Behavior (Default)

The pattern <.+> matches from the first < to the LAST >, grabbing everything in between. That's greedy!

Lazy Behavior

Add ? after the quantifier to make it lazy:

Now <.+?> matches each tag separately - it stops at the first > it finds.

Comparison

Greedy	Lazy	Behavior
*	*?	Zero or more (prefer fewer)
+	+?	One or more (prefer fewer)
?	??	Zero or one (prefer zero)
{n,m}	{n,m}?	Range (prefer fewer)

Exercises

Greedy Problems

Practical Example: Extract Values

Understanding the Difference

Think of it this way:

• Greedy: "Give me everything you can!"
• Lazy: "Give me the minimum required."

Greedy a.*b matches aXXXbYYYbZZZb (all the way to the last 'b').

Lazy a.*?b matches just aXXXb (stops at the first 'b').

When to Use Each

Use Greedy when:

• You want to match as much as possible
• There's only one possible ending point

Use Lazy when:

• You have repeating patterns
• You want the shortest match
• Parsing structured data (HTML, JSON, etc.)

Alternative: Negated Sets

Often, a negated character set is cleaner than lazy matching:

Practice Playground

Compare:

• <.*> vs <.*?>
• ".*" vs ".*?"
• \(.*\) vs \(.*?\)

Key Takeaways

• Greedy quantifiers (*, +, ?) match as much as possible
• Add ? to make them lazy: *?, +?, ??
• Lazy quantifiers match as little as possible
• Negated sets [^x]* often work better than lazy matching
• Use lazy matching when parsing repeated patterns