C ++在不使用正则表达式的情况下获取自定义分隔符之间的子字符串

Question

我有一个简单的格式字符串：

"lorem ipsum <span id='1'>extract_me-1</span> dolor
sit amet <span id='2'>extract_me-2</span> adispicing consequit lorem ipsum
sit amet <span id='3'>extract_me-3</span> adispicing dolor lorem"

现在我需要提取指定的自定义分隔符之间的字符串

例如，

Substring("<span id='1'>","</span>") = extract_me-1
Substring("<span id='2'>","</span>") = extract_me-2
Substring("lorem","<span id='1'>") = ipsum
Substring("extract_me-1","dolor") = </span>

我已经使用正则表达式完成了这项任务：

std::string str="lorem ipsum <span id='1'>extract_me-1</span> dolor sit amet <span id='2'>extract_me-2</span> adispicing consequit lorem ipsum sit amet <span id='3'>extract_me-3</span> adispicing dolor lorem";

std::smatch match;
std::regex rgx ("<span id='1'>(.*?)</span>");

if (regex_search(str, match, rgx)){
 //First substring
 std::cout<<match.str(1);
}

有没有不使用正则表达式的方法来做到这一点。我已经尝试使用 substr 几次，但仍然无济于事。非常感谢您的帮助，thnks

编辑：输入 str 不是完整的 html 格式，只是一些随机标签。我只需要从开始到 下一个最接近的子字符串结束位置（是的，即使有相同 span 或重复的嵌套标签）

Answer 1

您需要检查每个 str.find() 调用的每个 return 值，就像我对第一个调用所做的那样，但这是它的要点。可能只想搜索标签，然后搜索 ID，但随后您还需要检查该标签的不存在 ID：

#include <string>


int main() {
    const std::string str="lorem ipsum <span id='1'>extract_me-1</span> dolor sit amet <span id='2'>extract_me-2</span> adispicing consequit lorem ipsum sit amet <span id='3'>extract_me-3</span> adispicing dolor lorem";
    const std::string tag = "<span id='";
    std::string r = "";
    for(size_t pos = 0;;) {
        size_t tag_pos = str.find(tag, pos);
        if(tag_pos  == str.npos) {
            break;
        }
        size_t id_pos = tag_pos + tag.size();
        size_t id_pos2 = str.find("'", id_pos);
        size_t txt_pos = str.find(">", id_pos2) + 1;
        size_t txt_pos2 = str.find("<", txt_pos);

        r += "txt";
        r += str.substr(id_pos, id_pos2 - id_pos);
        r += " = ";
        r += str.substr(txt_pos, txt_pos2 - txt_pos);
        r += "\n";

        pos = txt_pos2;
    }
}

Answer 2

我使用 .find 和 .substr 解决了这个问题。结果比我想象的要容易

#include <string>
#include <iostream>

using namespace std;

int t1,t2;
string str="lorem ipsum <span id='1'>extract_me-1</span> dolor sit amet <span id='2'>extract_me-2</span> adispicing consequit lorem ipsum sit amet <span id='3'>extract_me-3</span> adispicing dolor lorem";

string subStrng(string start,string end);

int main() {
    string txt1 = subStrng("<span id='1'>","</span>");
    string txt2 = subStrng("<span id='2'>","</span>");
    string txt3 = subStrng("<span id='3'>","</span>");

    cout<<txt1<<"\n"<<txt2<<"\n"<<txt3;
    return 0;
}


//Substring func.
string subStrng(string start,string end){
    t1=str.find(start);
    if(t1 >= 0){
        // string 'start' exist in str.
        // Now, lets find the next closest string 'end'
        t1=t1+start.length();
        t2=str.find(end,t1);
        if(t2 >= 0){
            // next closest 'end' exists in the str.
            // Now, lets extract the substring in between
            return str.substr(t1,t2-t1);

        }else{
            return "";
        }
    }else{
        return "";
    }
}

干杯

C ++在不使用正则表达式的情况下获取自定义分隔符之间的子字符串

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