The match_results::length() is a inbuilt function in C++ which is used to return the length of a particular match in the match_results object.
Syntax:
smatch_name.length(n) Note: smatch_name is an object of match_results class.
Parameters: It accepts a single parameter n which specifies the Match number. It is lower than match_results::size. The match number 0 represents the entire matched expression. Subsequent match numbers identify the sub-expressions if any. The passed integral is an unsigned integral type.
Return Value:It returns the length of the n-th match in the match_results object.
Note: First element always contains the whole regex match while the others conatain the particular Capturing Group.
Below programs illustrate the above function.
Program 1:
// CPP program to illustrate // match_results length() in C++ #include <bits/stdc++.h> using namespace std; int main() { string s("Geeksforgeeks"); regex re("(Geeks)(.*)"); smatch match; regex_match(s, match, re); for (int i = 0; i < match.size(); i++) { cout << "match " << i << " has a length of " << match.length(i) << endl; } return 0; } |
match 0 has a length of 13 match 1 has a length of 5 match 2 has a length of 8
Program 2:
// CPP program to illustrate // match_results length() in C++ #include <bits/stdc++.h> using namespace std; int main() { string s("Geeksforgeeks"); regex re("(Ge)(eks)(.*)"); smatch match; regex_match(s, match, re); int max_length = 0; string str; // Since the first match is the // whole string we do not consider it. for (int i = 1; i < match.size(); i++) { if (match.length(i) > max_length) { str = match[i]; max_length = match.length(i); } } cout << "max-length sub match is " << str << " with a length of " << max_length; return 0; } |
max-length sub match is forgeeks with a length of 8
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