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

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。

其他回答

这是一个简单的stl解决方案(~5行!)使用std::find和std::find_first_not_of来处理重复的分隔符(例如空格或句号),以及开头和结尾的分隔符:

#include <string>
#include <vector>

void tokenize(std::string str, std::vector<string> &token_v){
    size_t start = str.find_first_not_of(DELIMITER), end=start;

    while (start != std::string::npos){
        // Find next occurence of delimiter
        end = str.find(DELIMITER, start);
        // Push back the token found into vector
        token_v.push_back(str.substr(start, end-start));
        // Skip all occurences of the delimiter to find new start
        start = str.find_first_not_of(DELIMITER, end);
    }
}

现场试试吧!

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。

/// 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。

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;
    }
}

这是一个非常简单的问题:

#include <vector>
#include <string>
using namespace std;

vector<string> split(const char *str, char c = ' ')
{
    vector<string> result;

    do
    {
        const char *begin = str;

        while(*str != c && *str)
            str++;

        result.push_back(string(begin, str));
    } while (0 != *str++);

    return result;
}