看了一圈答案没有用STD Map解的，自己写踩了不少坑，尤其是当系数等于1….属实是没想到了

中间很多代码重复的，懒得再解耦了

#include <bits/stdc++.h>

int main() {
    std::map<long long, long long> final;
    for (int i = 0; i < 2; ++i) {
        std::string result = "";
        while (true) {
            long long a, b;
            std::cin >> a >> b;
            // 判断是否结束
            if (a == 0 && b == -1) {
                break;
            }

            if (a == 0) {
                continue;
            }
            // 判断该指数是否存在
            if (final.find(b) == final.end()) {
                final.insert(std::make_pair(b, a));
            } else {
                long long new_a = final.find(b)->second + a;
                if (new_a == 0) {
                    final.erase(b);
                } else {
                    final.find(b)->second = new_a;
                }
            }

            // 判断是否为第一项，不是则加+号
            if (result.length() != 0 && a > 0) {
                result = result.append("+");
            }
            // 判断是否为常数项
            if (b == 0) {
                result = result.append(std::to_string(a));
                continue;
            }

            if (b == 1) {
                if (a == 1) {
                    result = result.
                            append("X");
                    continue;
                } else if (a == -1) {
                    result = result.
                            append("-X");
                    continue;
                }

                result = result.
                        append(std::to_string(a)).
                        append("X");
            } else {

                if (a == 1) {
                    result = result.
                            append("X^").
                            append(std::to_string(b));
                    continue;
                } else if (a == -1) {
                    result = result.
                            append("-X^").
                            append(std::to_string(b));
                    continue;
                }

                result = result.
                        append(std::to_string(a)).
                        append("X^").
                        append(std::to_string(b));
            }
        }
        if (result.length() == 0) {
            result = "0";
        }
        std::cout << result << std::endl;
    }

    std::map<long long, long long>::reverse_iterator iterator;
    std::string result = "";

    for (iterator = final.rbegin(); iterator != final.rend(); iterator++) {
        if (iterator != final.rbegin() && iterator->second > 0) {
            result = result.append("+");
        }

        if (iterator->first == 0) {
            result = result.append(std::to_string(iterator->second));
            continue;
        }

        if (iterator->first == 1) {
            if (iterator->second == 1) {
                result = result.
                        append("X");
                continue;
            } else if (iterator->second == -1) {
                result = result.
                        append("-X");
                continue;
            }

            result = result.
                    append(std::to_string(iterator->second)).
                    append("X");
        } else {

            if (iterator->second == 1) {
                result = result.
                        append("X^").
                        append(std::to_string(iterator->first));
                continue;
            } else if (iterator->second == -1) {
                result = result.
                        append("-X^").
                        append(std::to_string(iterator->first));
                continue;
            }


            result = result.
                    append(std::to_string(iterator->second)).
                    append("X^").
                    append(std::to_string(iterator->first));
        }
    }

    if (result.length() == 0) {
        result = "0";
    }

    std::cout << result << std::endl;

    return 0;
}