C++ match_results operator[]用法及代码示例

match_results::operator []是C++中的内置函数，用于获取match_result对象中的i-th匹配项。它为操作员内部指定位置的匹配提供参考。

用法:

smatch_name[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：它在N-th匹配处返回对该匹配的直接引用。

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 operator[] in C++ 
#include <bits/stdc++.h> 
using namespace std; 
  
int main() 
{ 
    string s("Geeksforgeeks"); 
    regex re("(Geeks)(.*)"); 
  
    smatch match; 
  
    regex_match(s, match, re); 
  
    // use of operator[]--> returns the 
    // reference to the match at i-th position 
    cout << "Matches are:" << endl; 
    for (int i = 0; i < match.size(); i++) { 
        cout << "match " << i << " is " << match[i] << endl; 
    } 
}

输出：

Matches are:
match 0 is Geeksforgeeks
match 1 is Geeks
match 2 is forgeeks

程序2:

// CPP program to illustrate 
// match_results operator[] in C++ 
// Find maximum length  
#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 << endl; 
    return 0; 
}

输出：

max-length sub match is forgeeks with a length of 8

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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 operator[] 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。