CODEWITHSUNDEEP
c++regex
user6882413
user6882413

Reputation: 341

Optional search with regular expression

I have a string "minDate=2013-12-01T08:00:00Z&maxDate=2014-01-01T12:00:00Z" So i need the min and max date in output. The Regex which i use is "minDate=(.*?)(?:maxDate=)(.*)"

I get the correct output : 

Full match  `minDate=2013-12-01T08:00:00Z&maxDate=2014-01-01T12:00:00Z`  
Group 1.    `2013-12-01T08:00:00Z;`  
Group 2.    `2014-01-01T12:00:00Z`

Now the problem is "minDate" or "maxDate" can be optional. Means the input can be either: 

minDate=2013-12-01T08:00:00Z&maxDate=2014-01-01T12:00:00Z

or 

minDate=2013-12-01T08:00:00Z

or 

maxDate=2014-01-01T12:00:00Z

What will be the Regex for this so that:

for first input i should get Group 1 '2013-12-01T08:00:00Z' and Group 2 as '2014-01-01T12:00:00Z'
and for second input i should get Group1 '2013-12-01T08:00:00Z'
and for third input i should get Group1 '2014-01-01T12:00:00Z'

Upvotes: 1

Views: 99

Answers (1)

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 626893

You may match and capture minDate or maxDate into Group 1 and the datetime value into Group 2, and then you can assign the variables in your program as needed:

std::string maxDate = "";
std::string minDate = "";
std::regex r("(min|max)Date=([0-9-]+T[0-9A-Z:]+)");
std::string s = "minDate=2013-12-01T08:00:00Z&maxDate=2014-01-01T12:00:00Z";
for(std::sregex_iterator i = std::sregex_iterator(s.begin(), s.end(), r);
    i != std::sregex_iterator();
    ++i)
{
    std::smatch m = *i;
    if (m[1].str()=="min") {
        minDate = m[2].str();
        std::cout << "Min date: " << minDate << endl;
    } else {
        maxDate = m[2].str();
        std::cout << "Max date: " << maxDate << endl;
    }
}

See the C++ demo

Output:

Min date: 2013-12-01T08:00:00Z
Max date: 2014-01-01T12:00:00Z

Pattern details

  • (min|max) - Capturing group 1 (this value is checked against): either min or max
  • Date= - a literal string Date=
  • ([0-9-]+T[0-9A-Z:]+) - Capturing group 2 (its value is the result): one or more digits or/and -, then T, then one or more uppercase ASCII letters, digits or/and :.

Upvotes: 1

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