我如何在c++中标记一个字符串?

Java有一个方便的分割方法:

String str = "The quick brown fox";
String[] results = str.split(" ");

在c++中有简单的方法来做到这一点吗?

当前回答

无意冒犯，但对于这样一个简单的问题，你把事情搞得太复杂了。使用Boost有很多理由。但对于这么简单的事情，就像用20号雪橇打苍蝇一样。

void
split( vector<string> & theStringVector,  /* Altered/returned value */
       const  string  & theString,
       const  string  & theDelimiter)
{
    UASSERT( theDelimiter.size(), >, 0); // My own ASSERT macro.

    size_t  start = 0, end = 0;

    while ( end != string::npos)
    {
        end = theString.find( theDelimiter, start);

        // If at end, use length=maxLength.  Else use length=end-start.
        theStringVector.push_back( theString.substr( start,
                       (end == string::npos) ? string::npos : end - start));

        // If at end, use start=maxSize.  Else use start=end+delimiter.
        start = (   ( end > (string::npos - theDelimiter.size()) )
                  ?  string::npos  :  end + theDelimiter.size());
    }
}

例如(以Doug为例)，

#define SHOW(I,X)   cout << "[" << (I) << "]\t " # X " = \"" << (X) << "\"" << endl

int
main()
{
    vector<string> v;

    split( v, "A:PEP:909:Inventory Item", ":" );

    for (unsigned int i = 0;  i < v.size();   i++)
        SHOW( i, v[i] );
}

是的，我们可以split()返回一个新的向量，而不是传入一个。包装和重载是很简单的。但根据我所做的事情，我经常发现重用已有的对象比总是创建新对象更好。(只要我不忘记清空中间的向量!)

参考:http://www.cplusplus.com/reference/string/string/。

(我最初是在写一个回应Doug的问题:基于分隔符的c++字符串修改和提取(关闭)。但由于马丁·约克用这里的指针结束了这个问题……我将泛化我的代码。)

2008-11-28 02:55:51

其他回答

请看这个例子。它可能对你有帮助。

#include <iostream>
#include <sstream>

using namespace std;

int main ()
{
    string tmps;
    istringstream is ("the dellimiter is the space");
    while (is.good ()) {
        is >> tmps;
        cout << tmps << "\n";
    }
    return 0;
}

2010-12-20 12:25:35

/// split a string into multiple sub strings, based on a separator string
/// for example, if separator="::",
///
/// s = "abc" -> "abc"
///
/// s = "abc::def xy::st:" -> "abc", "def xy" and "st:",
///
/// s = "::abc::" -> "abc"
///
/// s = "::" -> NO sub strings found
///
/// s = "" -> NO sub strings found
///
/// then append the sub-strings to the end of the vector v.
/// 
/// the idea comes from the findUrls() function of "Accelerated C++", chapt7,
/// findurls.cpp
///
void split(const string& s, const string& sep, vector<string>& v)
{
    typedef string::const_iterator iter;
    iter b = s.begin(), e = s.end(), i;
    iter sep_b = sep.begin(), sep_e = sep.end();

    // search through s
    while (b != e){
        i = search(b, e, sep_b, sep_e);

        // no more separator found
        if (i == e){
            // it's not an empty string
            if (b != e)
                v.push_back(string(b, e));
            break;
        }
        else if (i == b){
            // the separator is found and right at the beginning
            // in this case, we need to move on and search for the
            // next separator
            b = i + sep.length();
        }
        else{
            // found the separator
            v.push_back(string(b, i));
            b = i;
        }
    }
}

boost库很好，但并不总是可用的。手工做这些事情也是很好的脑力锻炼。这里我们只使用STL中的std::search()算法，参见上面的代码。

2014-02-25 06:40:51

Boost有很强的拆分功能:Boost::algorithm::split。

示例程序:

#include <vector>
#include <boost/algorithm/string.hpp>

int main() {
    auto s = "a,b, c ,,e,f,";
    std::vector<std::string> fields;
    boost::split(fields, s, boost::is_any_of(","));
    for (const auto& field : fields)
        std::cout << "\"" << field << "\"\n";
    return 0;
}

输出:

"a"
"b"
" c "
""
"e"
"f"
""

2008-09-12 17:20:23

我知道这个问题已经有了答案，但我想有所贡献。也许我的解决方案有点简单，但这就是我想到的:

vector<string> get_words(string const& text, string const& separator)
{
    vector<string> result;
    string tmp = text;

    size_t first_pos = 0;
    size_t second_pos = tmp.find(separator);

    while (second_pos != string::npos)
    {
        if (first_pos != second_pos)
        {
            string word = tmp.substr(first_pos, second_pos - first_pos);
            result.push_back(word);
        }
        tmp = tmp.substr(second_pos + separator.length());
        second_pos = tmp.find(separator);
    }

    result.push_back(tmp);

    return result;
}

如果在我的代码中有更好的方法，或者有什么错误，请评论。

更新:添加通用分隔符

2018-05-09 07:12:21