用C++ 语言如何实现表达式拆分“1*2*3*(4+(5+6)*(7+8))+9”

问题：用C++ 语言如何实现表达式拆分
把一个字符串形式的数学表达式以拆加号为原则，一级一级拆分，最终汇总为一个字符串数组。数学表达式是由”+”、”(“、”)”和数字组成。

示例如下：

1、字符串表达式为：1*2*3*(4+(5+6)*(7+8))+9

拆分最终的字符串数组结果为（数组元素排序没有要求）：
1*2*3*4
1*2*3*5*7
1*2*3*5*8
1*2*3*6*7
1*2*3*6*8
9

// C++11

代码如下：

#include <iostream>#include <string>#include <vector>std::vector<std::string> processexp(const std::string &sexp);int main(){        std::string sexp;        std::getline(std::cin, sexp);        std::cout << sexp << std::endl;        std::vector<std::string> svret = processexp(sexp);        for (const auto &i : svret) {                std:: cout << i << std::endl;        }        return 0;}std::vector<std::string> processexp(const std::string &sexp){        std::vector<std::string> svec;        std::vector<std::string> destsvec;        std::vector<std::string> midsvec;        std::string read;        char c;        for (std::string::size_type i = 0; i < sexp.size(); i++) {                c = sexp[i];                switch (c) {                case '*':                        {                        if (!read.empty()) {                                svec.push_back(read);                                read.clear();                        }                        svec.emplace_back(1, c);                        }                        break;                case '(':                        {                        std::string::size_type m, n, p1, p2;                        m = i;                        while (true) {                                m += 1;                                p1 = sexp.find_first_of('(', m);                                p2 = sexp.find_first_of(')', m);                                if (p1 != std::string::npos && p1 < p2) {                                        m = p2;                                        continue;                                }                                n = p2;                                break;                        }                        std::string subexp = sexp.substr(i+1, n - i - 1);                        std::vector<std::string> sv = processexp(subexp);                        if (i > 1 && sexp[i-1] != '*'                                && n + 1 < sexp.size() && sexp[n+1] == '*') {                                midsvec = sv;                                i = n;                                break;                        }                        std::string bfexp;                        for (const auto &e : svec) {                                bfexp += e;                        }                        svec.clear();                        std::vector<std::string> desttemp{midsvec};                        midsvec.clear();                        for (const auto &e : sv) {                                if (!desttemp.empty()) {                                        for (const auto &e2 : desttemp) {                                                auto e3 = e2 + bfexp + e;                                                midsvec.push_back(e3);                                        }                                } else {                                        midsvec.push_back(bfexp+e);                                }                        }                        if (n + 1 < sexp.size() && sexp[n+1] == '*') {#if 0                                for (const auto &e : destsvec) {                                        std::cout << "|<<<" << e << "|";                                }                                std::cout << std::endl;#endif                        } else {                                destsvec.insert(destsvec.end(), midsvec.begin(), midsvec.end());                                midsvec.clear();                        }                        i = n;                        }                        break;                case '+':                        {                        if (!read.empty()) {                                svec.push_back(read);                        }                        std::string all;                        for (const auto &e : svec) {                                all += e;                        }                        if (!all.empty()) {                                std::vector<std::string> desttemp{midsvec};                                midsvec.clear();                                if (!desttemp.empty()) {                                        for (const auto &e2 : desttemp) {                                                auto e3 = e2 + all;                                                destsvec.push_back(e3);                                        }                                } else {                                        destsvec.push_back(all);                                }                        }                        svec.clear();                        read.clear();                        }                        break;                default:                        read += c;                        break;                }        }        if (!read.empty()) {                svec.push_back(read);        }        std::string all;        for (const auto &e : svec) {                all += e;        }        if (!all.empty()) {                std::vector<std::string> desttemp{midsvec};                midsvec.clear();                if (!desttemp.empty()) {                        for (const auto &e2 : desttemp) {                                auto e3 = e2 + all;                                destsvec.push_back(e3);                        }                } else {                        destsvec.push_back(all);                }        }        return destsvec;}