Two ways to split strings in C++

The frequency of string cutting is still quite high. The string itself does not provide a cutting method, but it can be implemented using the package provided by stl or through the c function strtok() function.

1. Implemented through stl

Two functions of the string class, find and substr, are involved: 
1. The prototype of the find function 
: size_t find ( const string& str, size_t pos = 0 ) const; 
Function: Find the first occurrence of a substring. 
Parameter description: str is a substring, and pos is the initial search position. 
Return value: if found, return the position of the first occurrence, otherwise return string::npos

2. Substr function 
prototype: string substr ( size_t pos = 0, size_t n = npos ) const; 
Function: Get the substring. 
Parameter description: pos is the start position (default is 0), n is the end position (default is npos) 
Return value: The substring 
code is as follows:

1 std::vector<std:: string > splitWithStl( const std:: string &str, const std:: string & pattern)
 2  {
 3      std::vector<std:: string > resVec;
 4  
5      if ( "" = = str)
 6      {
 7          return resVec;
 8      }
 9      // Convenient to intercept the last piece of data 
10      std:: string strs = str + pattern;
 11  
12      size_t pos = strs.find(pattern);
13     size_t size = strs.size();
14 
15     while (pos != std::string::npos)
16     {
17         std::string x = strs.substr(0,pos);
18         resVec.push_back(x);
19         strs = strs.substr(pos+1,size);
20         pos = strs.find(pattern);
21     }
22 
23     return resVec;
24 }

2. By using strtok() function

原型：char *strtok(char *str, const char *delim); 
功能：分解字符串为一组字符串。s为要分解的字符串，delim为分隔符字符串。 
描述：strtok()用来将字符串分割成一个个片段。参数s指向欲分割的字符串，参数delim则为分割字符串，当strtok()在参数s的字符串中发现到参数delim的分割字符时 则会将该字符改为\0 字符。在第一次调用时，strtok()必需给予参数s字符串，往后的调用则将参数s设置成NULL。每次调用成功则返回被分割出片段的指针。

其它：strtok函数线程不安全，可以使用strtok_r替代。 
代码如下：

vector<string> split(const string &str,const string &pattern)
{
    //const char* convert to char*
    char * strc = new char[strlen(str.c_str())+1];
    strcpy(strc, str.c_str());
    vector<string> resultVec;
    char* tmpStr = strtok(strc, pattern.c_str());
    while (tmpStr != NULL)
    {
        resultVec.push_back(string(tmpStr));
        tmpStr = strtok(NULL, pattern.c_str());
    }

    delete[] strc;

    return resultVec;
}