字符串分割C++

int to_int(std::string& strInput)
{
    int nReturn = 0;
    std::stringstream ss;
    ss << strInput;
    ss >> nReturn;
    return nReturn;
}
int getNumFromString(std::string& strChannelNo, int nIndex)
{
    std::vector<std::string> vResults;
    int start = 0;
    int end = strChannelNo.find("_");//待分割的字符串
    int delimiter_len = 1;//待分割的字符串长度

    while (end != std::string::npos) {
        std::string token = strChannelNo.substr(start, end - start);
        if (!token.empty()) {
            vResults.push_back(token);
        }
        start = end + delimiter_len;
        end = strChannelNo.find("_", start);
    }

    // 添加最后一个子串
    std::string lastToken = strChannelNo.substr(start);
    if (!lastToken.empty()) {
        vResults.push_back(lastToken);
    }
    return to_int(vResults[nIndex - 1]);
}