正则表达式（Java，C#，C++）

课题

1. 使用正则表达式匹配字符串
   使用正则表达式 "d{3}-(d{4})-d{2}" 匹配字符串 "123-4567-89"
   返回匹配结果：’"123-4567-89" 以及 "4567"
2. 使用正则表达式替换字符串（模式）
   使用正则表达式 "(d+)-(d+)-(d+)" 匹配字符串 "123-4567-89"
   使用模式字符串 "$3-$1-$2" 替换匹配结果，返回结果 "89-123-4567"。
3. 使用正则表达式替换字符串（回调）
   使用正则表达式 "d+" 匹配字符串 "123-4567-89"
   将匹配结果即三个数字串全部翻转过来，返回结果 "321-7654-98"。
4. 使用正则表达式分割字符串
   使用正则表达式 "%(begin|next|end)%" 分割字符串"%begin%hello%next%world%end%"
   返回正则表达式分隔符之间的两个字符串 "hello" 和 "world"。

Java

import java.util.Arrays;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Test {

    public static void main(String[] args) {
        String s = "123-4567-89,987-6543-21";
        Pattern r = Pattern.compile("\d{3}-(\d{4})-\d{2}");
        Matcher m = r.matcher(s);
        for (int i = 0; m.find(); i++) {
            if (i == 0)
                System.out.println("Found matches:");
            for (int j = 0; j <= m.groupCount(); j++)
                System.out.printf("group %d,%d : %s
", i, j, m.group(j));
        }
 
        System.out.println(s.replaceFirst("(\d+)-(\d+)-(\d+)", "$3-$1-$2"));
 
        // https://stackoverflow.com/questions/19737653/what-is-the-equivalent-of-regex-replace-with-function-evaluation-in-java-7
        r = Pattern.compile("\d+");
        m = r.matcher(s);
        StringBuffer sb = new StringBuffer();
        while (m.find())
            m.appendReplacement(sb, new StringBuffer(m.group(0)).reverse().toString());
        m.appendTail(sb);
        System.out.println(sb.toString());
 
        r = Pattern.compile("%(begin|next|end)%");
        s = "%begin%hello%next%world%end%";
        System.out.println(Arrays.asList(r.split(s)));
    }
}
 
/*
Found matches:
group 0,0 : 123-4567-89
group 0,1 : 4567
group 1,0 : 987-6543-21
group 1,1 : 6543
89-123-4567,987-6543-21
321-7654-98,789-3456-12
[, hello, world]
*/

C#

using System;
using System.Text.RegularExpressions;
 
namespace Sample
{
    class Test
    {
        public static void Main(string[] args)
        {
            var r = new Regex(@"d{3}-(d{4})-d{2}");
            var s = "123-4567-89,987-6543-21";
            {
                var m = r.Match(s);
                if (m.Success)
                    Console.WriteLine("Found matches:");
            }
            foreach (var (m, i) in r.Matches(s).Cast<Match>().Select((m, i) => (m, i)))
                foreach (var (g, j) in m.Groups.Cast<Group>().Select((g, j) => (g, j)))
                    Console.WriteLine($"group {i},{j} : {g.Value}");
 
            r = new Regex(@"(d+)-(d+)-(d+)");
            Console.WriteLine(r.Replace(s, "$3-$1-$2"));
            
            r = new Regex(@"d+");
            s = r.Replace(s, m2 => {
                var arr = m2.Groups[0].Value.ToCharArray();
                Array.Reverse(arr);
                return new string(arr);
            });
            Console.WriteLine(s);
 
            r = new Regex("%(?:begin|next|end)%");
            s = "%begin%hello%next%world%end%";
            Console.WriteLine(String.Join(",", r.Split(s)));
        }
    }
}
 
/*
Found matches:
group 0,0 : 123-4567-89
group 0,1 : 4567
group 1,0 : 987-6543-21
group 1,1 : 6543
89-123-4567,21-987-6543
321-7654-98,789-3456-12
,hello,world,
*/

C++

#include <iostream>
#include <string>
#include <vector>
#include <boost/regex.hpp>
#include <boost/algorithm/string.hpp>
using namespace std;

int main()
{
    string s = "123-4567-89,987-6543-21";
    boost::regex r(R"(d{3}-(d{4})-d{2})");
    boost::match_results<string::const_iterator> mr;
    if (boost::regex_search(s, mr, r))
        cout << "Found matches:" << endl;
    int i = 0;
    for (boost::sregex_iterator begin(s.begin(), s.end(), r), end, it = begin; it != end; ++it, ++i)
        for (size_t j = 0; j < it->size(); ++j)
            cout << "group " << i << "," << j << " : " << (*it)[j] << endl;
     
    boost::regex r2(R"((d+)-(d+)-(d+))");
    cout << boost::regex_replace(s, r2, "$3-$1-$2") << endl;
     
    boost::regex r3(R"(d+)");
    s = boost::regex_replace(s, r3, [](auto& match) {
        string s = match.str();
        reverse(s.begin(), s.end());
        return s;
    });
    cout << s << endl;
     
    boost::regex r4("%(?:begin|next|end)%");
    s = "%begin%hello%next%world%end%";
    vector<string> v;
    for (boost::sregex_token_iterator begin(s.begin(), s.end(), r4, -1), end, i = begin; i != end; ++i)
        v.push_back(i->str());
    cout << boost::algorithm::join(v, ",") << endl;
}

/*
Found matches:
group 0,0 : 123-4567-89
group 0,1 : 4567
group 1,0 : 987-6543-21
group 1,1 : 6543
89-123-4567,21-987-6543
321-7654-98,789-3456-12
,hello,world
*/