c++ 字符串切分split

c++ 字符串切分split 的举例实现
一共给出了四种方式
1、 strtok
2、 stringstream
3、 字符串查找
4、 基于封装的方式，提供了 c++11 foreach 接口

代码

vector<string> split(string s) {
    vector<string> res;
    const char *p = strtok((char *) s.c_str(), " ");
    res.push_back(p);
    while ((p = strtok(NULL, " "))) {
        res.push_back(p);
    }
    return res;
}

vector<string> split2(string s) {
    vector<string> res;
    stringstream ss(s);
    string tmp;
    while (ss >> tmp) {
        res.push_back(tmp);
    }
    return res;
}

vector<string> split3(string s) {
    vector<string> res;
    auto start = s.find_first_not_of(" ", 0);
    auto pos = s.find_first_of(" ", start);
    while (string::npos != start) {
        res.push_back(s.substr(start, pos - start));
        start = s.find_first_not_of(" ", pos);
        pos = s.find_first_of(" ", start);
    }
    return res;
}

class Splitor;

class SplitorIte {
private:
    Splitor *sp;
    string s;

public:
    static string splitorIteNULL;

    SplitorIte(Splitor *sp);

    SplitorIte();

    SplitorIte &operator++();

    string operator*() {
        return s;
    }

    bool operator!=(const SplitorIte &other) {
        return s != other.s;
    }
};


string SplitorIte::splitorIteNULL = "!!!!!!!";

class Splitor {
private:
    string s;
    unordered_set<char> des;
    int start = 0;
    bool allow_empty = false;
public:
    Splitor(const string &s, string delim, bool allow_empty = false) : s(s), des(delim.begin(), delim.end()),
                                                                       allow_empty(allow_empty) {}

    auto operator()() -> string {
        string res;
        do {
            int p = start;
            // 如果当前就是
            if (p >= s.size()) {
                return SplitorIte::splitorIteNULL;
            }
            if (allow_empty && des.count(s[p])) {
                start++;
                return "";
            }
            // 找到第一个非
            while (p < s.size() and des.count(s[p])) p++;
            if (p == s.size()) {
                return SplitorIte::splitorIteNULL;
            }
            // 找到第一个是
            int q = p + 1;
            while (q < s.size() and !des.count(s[q])) q++;
            res = s.substr(p, q - p);
            start = q + 1;
        } while (!allow_empty && res.empty());
        return res;
    }

    SplitorIte begin() {
        return {this};
    }

    SplitorIte end() {
        return {};
    }
};

SplitorIte::SplitorIte(Splitor *sp) : sp(sp) {
    s = (*sp)();
}

SplitorIte::SplitorIte() {
    sp = nullptr;
    s = splitorIteNULL;
}

SplitorIte &SplitorIte::operator++() {
    s = (*sp)();
    return *this;
};


int main() {
    cout << "允许出现空格：\n";
    string s = "a ssst";
    Splitor sp(s, "s", true);
    int i = 0;
    for (auto str: sp) {
        cout << i << "\t[" << str << "]" << endl;
        i++;
    }
    cout << "不允许出现空格：\n";
    Splitor esp(s, "s");
    i = 0;
    for (auto str: esp) {
        cout << i << "\t[" << str << "]" << endl;
        i++;
    }
}

输出