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++;}
}