match_results::length()是C++中的內置函數，用於返回match_results對象中特定匹配項的長度。
用法:
smatch_name.length(n) Note:smatch_name is an object of match_results class.
參數：它接受一個指定匹配編號的參數n。它小於match_results::size。匹配數字0表示整個匹配表達式。後續的匹配數字標識子表達式(如果有)。傳遞的積分是無符號積分類型。
返回值：它返回match_results對象中n-th匹配的長度。
注意：第一個元素始終包含整個正則表達式匹配項，而其他元素則包含特定的捕獲組。
以下示例程序旨在說明上述函數。
程序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;
}
輸出：
match 0 has a length of 13 match 1 has a length of 5 match 2 has a length of 8
程序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;
}
輸出：
max-length sub match is forgeeks with a length of 8
相關用法
注：本文由純淨天空篩選整理自Harsha_Mogali大神的英文原創作品 match_results length() in C++ STL。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。