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Answer:

X[A-Z]+

The new expression matches the same set of strings as the previous one, but does not capture the prefix of X characters.

Reluctant Quantifier

Regular Expression
String
Group 0
Group 1	Group 2	Group 3	Group 4

An quantifier in a regular expression may be greedy (the default), reluctant, or possesive. A reluctant quantifier does this:

Strings are matched from left to right one character at a time.
A reluctant quantifier matches as few characters as it can without preventing the rest of the regular expression from matching.

An quantifier is made reluctant by appending a question mark. The expression X+? matches X one or more times, but matches as few X as it can without preventing other quantifier from matching. For example, when the expression

(X+?)([A-Z]+)

matches the string

XXXX

the reluctant X+? could potentially match the entire string. But it matches as little as possible: the first X . The final [A-Z]+ of the expression matches the rest the string.

Reluctant quantifier are sometimes called lazy quantifier, because they match as little as possible.

QUESTION 18:

Here is a string: XXXXX

What parts of the string match the capture group in the following expressions?

(X+)[A-Z]+
(X+?)[A-Z]+