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

我只是看了所有的答案,找不到下一个前提条件的解决方案:

没有动态内存分配 不使用boost 不使用正则表达式 c++17标准

这就是我的解

#include <iomanip>
#include <iostream>
#include <iterator>
#include <string_view>
#include <utility>

struct split_by_spaces
{
    std::string_view      text;
    static constexpr char delim = ' ';

    struct iterator
    {
        const std::string_view& text;
        std::size_t             cur_pos;
        std::size_t             end_pos;

        std::string_view operator*() const
        {
            return { &text[cur_pos], end_pos - cur_pos };
        }
        bool operator==(const iterator& other) const
        {
            return cur_pos == other.cur_pos && end_pos == other.end_pos;
        }
        bool operator!=(const iterator& other) const
        {
            return !(*this == other);
        }
        iterator& operator++()
        {
            cur_pos = text.find_first_not_of(delim, end_pos);

            if (cur_pos == std::string_view::npos)
            {
                cur_pos = text.size();
                end_pos = cur_pos;
                return *this;
            }

            end_pos = text.find(delim, cur_pos);

            if (cur_pos == std::string_view::npos)
            {
                end_pos = text.size();
            }

            return *this;
        }
    };

    [[nodiscard]] iterator begin() const
    {
        auto start = text.find_first_not_of(delim);
        if (start == std::string_view::npos)
        {
            return iterator{ text, text.size(), text.size() };
        }
        auto end_word = text.find(delim, start);
        if (end_word == std::string_view::npos)
        {
            end_word = text.size();
        }
        return iterator{ text, start, end_word };
    }
    [[nodiscard]] iterator end() const
    {
        return iterator{ text, text.size(), text.size() };
    }
};

int main(int argc, char** argv)
{
    using namespace std::literals;
    auto str = " there should be no memory allocation during parsing"
               "  into words this line and you   should'n create any"
               "  contaner                  for intermediate words  "sv;

    auto comma = "";
    for (std::string_view word : split_by_spaces{ str })
    {
        std::cout << std::exchange(comma, ",") << std::quoted(word);
    }

    auto only_spaces = "                   "sv;
    for (std::string_view word : split_by_spaces{ only_spaces })
    {
        std::cout << "you will not see this line in output" << std::endl;
    }
}

其他回答

使用regex_token_iterators的解决方案:

#include <iostream>
#include <regex>
#include <string>

using namespace std;

int main()
{
    string str("The quick brown fox");

    regex reg("\\s+");

    sregex_token_iterator iter(str.begin(), str.end(), reg, -1);
    sregex_token_iterator end;

    vector<string> vec(iter, end);

    for (auto a : vec)
    {
        cout << a << endl;
    }
}

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;
}

下面是我的Swiss®军刀字符串标记器,用于用空格分隔字符串,处理单引号和双引号包装的字符串,以及从结果中剥离这些字符。我使用RegexBuddy 4。x生成大部分代码片段,但我添加了用于剥离引号和其他一些东西的自定义处理。

#include <string>
#include <locale>
#include <regex>

std::vector<std::wstring> tokenize_string(std::wstring string_to_tokenize) {
    std::vector<std::wstring> tokens;

    std::wregex re(LR"(("[^"]*"|'[^']*'|[^"' ]+))", std::regex_constants::collate);

    std::wsregex_iterator next( string_to_tokenize.begin(),
                                string_to_tokenize.end(),
                                re,
                                std::regex_constants::match_not_null );

    std::wsregex_iterator end;
    const wchar_t single_quote = L'\'';
    const wchar_t double_quote = L'\"';
    while ( next != end ) {
        std::wsmatch match = *next;
        const std::wstring token = match.str( 0 );
        next++;

        if (token.length() > 2 && (token.front() == double_quote || token.front() == single_quote))
            tokens.emplace_back( std::wstring(token.begin()+1, token.begin()+token.length()-1) );
        else
            tokens.emplace_back(token);
    }
    return tokens;
}

另一种快速方法是使用getline。喜欢的东西:

stringstream ss("bla bla");
string s;

while (getline(ss, s, ' ')) {
 cout << s << endl;
}

如果需要,可以创建一个简单的split()方法,返回vector<string>,即 真的有用。

您可以使用流、迭代器和复制算法来相当直接地做到这一点。

#include <string>
#include <vector>
#include <iostream>
#include <istream>
#include <ostream>
#include <iterator>
#include <sstream>
#include <algorithm>

int main()
{
  std::string str = "The quick brown fox";

  // construct a stream from the string
  std::stringstream strstr(str);

  // use stream iterators to copy the stream to the vector as whitespace separated strings
  std::istream_iterator<std::string> it(strstr);
  std::istream_iterator<std::string> end;
  std::vector<std::string> results(it, end);

  // send the vector to stdout.
  std::ostream_iterator<std::string> oit(std::cout);
  std::copy(results.begin(), results.end(), oit);
}