match_results::length()是C++中的内置函数，用于返回match_results对象中特定匹配项的长度。
用法:
smatch_name.length(n) Note:smatch_name is an object of match_results class.
参数：它接受一个指定匹配编号的参数n。它小于match_results::size。匹配数字0表示整个匹配表达式。后续的匹配数字标识子表达式(如果有)。传递的积分是无符号积分类型。
返回值：它返回match_results对象中n-th匹配的长度。
注意：第一个元素始终包含整个正则表达式匹配项，而其他元素则包含特定的捕获组。
以下示例程序旨在说明上述函数。
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;
}
输出：
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;
}
输出：
max-length sub match is forgeeks with a length of 8
相关用法
注：本文由纯净天空筛选整理自Harsha_Mogali大神的英文原创作品 match_results length() in C++ STL。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。