match_results size() in C++ STL
Last Updated :
21 Jun, 2021
The match_results size() is a inbuilt function in C++ which returns the number of matches ans sub-matches in the match_result object.
Syntax:
smatch_name.size()
Note: smatch_name is an object of match_results class.
Parameters: The function accept no parameters.
Return value: It returns the number of matches in the match_result object.
Note: First element always contains the whole regex match while the others contain the particular Capturing Group
Below programs illustrate the above function.
Program 1:
CPP
#include <bits/stdc++.h>
using namespace std;
int main()
{
string s( "Geeksforgeeks" );
regex re( "(Geeks)(.*)" );
smatch match;
regex_match(s, match, re);
cout << "match size is " << match.size() << endl;
return 0;
}
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Program 2:
CPP
#include <bits/stdc++.h>
using namespace std;
int main()
{
string s( "Geeksforgeeks" );
regex re( "(Geeks)(.*)" );
smatch match;
regex_match(s, match, re);
cout << "match size is " << match.size() << endl;
for ( int i = 0; i < match.size(); i++) {
cout << "match " << i << " has a length of "
<< match.length(i) << endl;
}
return 0;
}
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Output:
match size is 3
match 0 has a length of 13
match 1 has a length of 5
match 2 has a length of 8
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