我在c++中使用以下方法解析字符串:

using namespace std;

string parsed,input="text to be parsed";
stringstream input_stringstream(input);

if (getline(input_stringstream,parsed,' '))
{
     // do some processing.
}

使用单个字符分隔符进行解析是可以的。但是如果我想使用字符串作为分隔符呢?

例子:我想拆分:

scott>=tiger

用>=作为分隔符,这样我就可以得到斯科特和老虎。


当前回答

您可以使用std::string::find()函数来查找字符串分隔符的位置,然后使用std::string::substr()来获取一个令牌。

例子:

std::string s = "scott>=tiger";
std::string delimiter = ">=";
std::string token = s.substr(0, s.find(delimiter)); // token is "scott"

find(const string& str, size_t pos = 0)函数的作用是:返回字符串中str第一次出现的位置,如果没有找到则返回npos。 substr(size_t pos = 0, size_t n = npos)函数的作用是:返回对象的子字符串,从位置pos开始,长度npos。


如果你有多个分隔符,在你提取了一个标记之后,你可以删除它(包括分隔符)以继续后续的提取(如果你想保留原始字符串,只需使用s = s.s substr(pos + delimiter.length());):

s.erase(0, s.find(delimiter) + delimiter.length());

这样就可以轻松地循环获取每个令牌。

完整的示例

std::string s = "scott>=tiger>=mushroom";
std::string delimiter = ">=";

size_t pos = 0;
std::string token;
while ((pos = s.find(delimiter)) != std::string::npos) {
    token = s.substr(0, pos);
    std::cout << token << std::endl;
    s.erase(0, pos + delimiter.length());
}
std::cout << s << std::endl;

输出:

scott
tiger
mushroom

其他回答

#include<iostream>
#include<algorithm>
using namespace std;

int split_count(string str,char delimit){
return count(str.begin(),str.end(),delimit);
}

void split(string str,char delimit,string res[]){
int a=0,i=0;
while(a<str.size()){
res[i]=str.substr(a,str.find(delimit));
a+=res[i].size()+1;
i++;
}
}

int main(){

string a="abc.xyz.mno.def";
int x=split_count(a,'.')+1;
string res[x];
split(a,'.',res);

for(int i=0;i<x;i++)
cout<<res[i]<<endl;
  return 0;
}

注:仅当分割后的字符串长度相等时才有效

Strtok允许您传入多个字符作为分隔符。我敢打赌,如果你传入“>=”,你的示例字符串将被正确分割(即使>和=被算作单独的分隔符)。

EDIT如果您不想使用c_str()将字符串转换为char*,您可以使用substr和find_first_of进行标记化。

string token, mystring("scott>=tiger");
while(token != mystring){
  token = mystring.substr(0,mystring.find_first_of(">="));
  mystring = mystring.substr(mystring.find_first_of(">=") + 1);
  printf("%s ",token.c_str());
}

还有另一个答案:这里我使用find_first_not_of字符串函数,它返回第一个不匹配delim中指定的任何字符的位置。

size_t find_first_not_of(const string& delim, size_t pos = 0) const noexcept;

例子:

int main()
{
    size_t start = 0, end = 0;
    std::string str = "scott>=tiger>=cat";
    std::string delim = ">=";
    while ((start = str.find_first_not_of(delim, end)) != std::string::npos)
    {
        end = str.find(delim, start); // finds the 'first' occurance from the 'start'
        std::cout << str.substr(start, end - start)<<std::endl; // extract substring
    }
    return 0;
}

输出:

    scott
    tiger
    cat

作为奖励,这里有一个分割函数和宏的代码示例,很容易使用,你可以在其中选择容器类型:

#include <iostream>
#include <vector>
#include <string>

#define split(str, delim, type) (split_fn<type<std::string>>(str, delim))
 
template <typename Container>
Container split_fn(const std::string& str, char delim = ' ') {
    Container cont{};
    std::size_t current, previous = 0;
    current = str.find(delim);
    while (current != std::string::npos) {
        cont.push_back(str.substr(previous, current - previous));
        previous = current + 1;
        current = str.find(delim, previous);
    }
    cont.push_back(str.substr(previous, current - previous));
    
    return cont;
}

int main() {
    
    auto test = std::string{"This is a great test"};
    auto res = split(test, ' ', std::vector);
    
    for(auto &i : res) {
        std::cout << i << ", "; // "this", "is", "a", "great", "test"
    }
    
    
    return 0;
}

下面是一个使用Boost string Algorithms库和Boost Range库将一个字符串与另一个字符串分割的示例。这个解决方案的灵感来自StringAlgo库文档,请参阅Split部分。

下面是split_with_string函数的完整程序,以及全面的测试-用godbolt试试:

#include <iostream>
#include <string>
#include <vector>
#include <boost/algorithm/string.hpp>
#include <boost/range/iterator_range.hpp>

std::vector<std::string> split_with_string(std::string_view s, std::string_view search) 
{
    if (search.empty()) return {std::string{s}};

    std::vector<boost::iterator_range<std::string_view::iterator>> found;
    boost::algorithm::ifind_all(found, s, search);
    if (found.empty()) return {};

    std::vector<std::string> parts;
    parts.reserve(found.size() + 2); // a bit more

    std::string_view::iterator part_begin = s.cbegin(), part_end;
    for (auto& split_found : found)
    {
        // do not skip empty extracts
        part_end = split_found.begin();
        parts.emplace_back(part_begin, part_end);
        part_begin = split_found.end();
    }
    if (part_end != s.end())
        parts.emplace_back(part_begin, s.end());

    return parts;
}

#define TEST(expr) std::cout << ((!(expr)) ? "FAIL" : "PASS") << ": " #expr "\t" << std::endl

int main()
{
    auto s0 = split_with_string("adsf-+qwret-+nvfkbdsj", "");
    TEST(s0.size() == 1);
    TEST(s0.front() == "adsf-+qwret-+nvfkbdsj");
    auto s1 = split_with_string("adsf-+qwret-+nvfkbdsj", "-+");
    TEST(s1.size() == 3);
    TEST(s1.front() == "adsf");
    TEST(s1.back() == "nvfkbdsj");
    auto s2 = split_with_string("-+adsf-+qwret-+nvfkbdsj-+", "-+");
    TEST(s2.size() == 5);
    TEST(s2.front() == "");
    TEST(s2.back() == "");
    auto s3 = split_with_string("-+adsf-+qwret-+nvfkbdsj", "-+");
    TEST(s3.size() == 4);
    TEST(s3.front() == "");
    TEST(s3.back() == "nvfkbdsj");
    auto s4 = split_with_string("adsf-+qwret-+nvfkbdsj-+", "-+");
    TEST(s4.size() == 4);
    TEST(s4.front() == "adsf");
    TEST(s4.back() == "");
    auto s5 = split_with_string("dbo.abc", "dbo.");
    TEST(s5.size() == 2);
    TEST(s5.front() == "");
    TEST(s5.back() == "abc");
    auto s6 = split_with_string("dbo.abc", ".");
    TEST(s6.size() == 2);
    TEST(s6.front() == "dbo");
    TEST(s6.back() == "abc");
}

测试输出:

PASS: s0.size() == 1    
PASS: s0.front() == "adsf-+qwret-+nvfkbdsj" 
PASS: s1.size() == 3    
PASS: s1.front() == "adsf"  
PASS: s1.back() == "nvfkbdsj"   
PASS: s2.size() == 5    
PASS: s2.front() == ""  
PASS: s2.back() == ""   
PASS: s3.size() == 4    
PASS: s3.front() == ""  
PASS: s3.back() == "nvfkbdsj"   
PASS: s4.size() == 4    
PASS: s4.front() == "adsf"  
PASS: s4.back() == ""   
PASS: s5.size() == 2    
PASS: s5.front() == ""  
PASS: s5.back() == "abc"    
PASS: s6.size() == 2    
PASS: s6.front() == "dbo"   
PASS: s6.back() == "abc"