字符串中的TRIM操作

std::string& ltrim(std::string& str, const std::string& chars = "	
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std::string& rtrim(std::string& str, const std::string& chars = "	
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std::string& trim(std::string& str, const std::string& chars = "	
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 ");

std::string& ltrim(std::string& str, const std::string& chars)
{
    str.erase(0, str.find_first_not_of(chars));
    return str;
}
 
std::string& rtrim(std::string& str, const std::string& chars)
{
    str.erase(str.find_last_not_of(chars) + 1);
    return str;
}
 
std::string& trim(std::string& str, const std::string& chars)
{
    return ltrim(rtrim(str, chars), chars);
}