Многочлены

#include <iostream>
#include <map>
#include <fstream>

using namespace std;

int main() {
    ifstream cin("polynomial.in");
    ofstream cout("polynomial.out");
    int n;
    cin >> n;
    for (int i = 0; i < n; i++) {
        map<pair<long, long>, long> NM;
        string expr;
        cin >> expr;
        long koeff = 1;
        long stN = 0;
        long stM = 0;
        unsigned int pos = 0;
        if (expr[0] == '-') {
            koeff = -1;
            pos++;
        }
        for (; pos < expr.length(); pos++) {
            switch (expr[pos]) {
                case '-': {
                    NM[make_pair(stN, stM)] += koeff;
                    koeff = -1;
                    stN = 0;
                    stM = 0;
                    break;
                }
                case '+': {
                    NM[make_pair(stN, stM)] += koeff;
                    koeff = 1;
                    stN = 0;
                    stM = 0;
                    break;
                }
                case '*': {
                    break;
                }
                case '^': {
                    int prevPos = pos - 1;
                    string s;
                    while (pos + 1 < expr.length() && '0' <= expr[pos + 1] && expr[pos + 1] <= '9') {
                        s += expr[pos + 1];
                        pos++;
                    }
                    if (expr[prevPos] == 'n') {
                        stN += stol(s);
                    } else {
                        stM += stol(s);
                    }
                    break;
                }
                case 'n': {
                    if (pos + 1 >= expr.length() || expr[pos + 1] != '^') {
                        stN++;
                    }
                    break;
                }
                case 'm': {
                    if (pos + 1 >= expr.length() || expr[pos + 1] != '^') {
                        stM++;
                    }
                    break;
                }
                default: {
                    string s;
                    while (pos < expr.length() && '0' <= expr[pos] && expr[pos] <= '9') {
                        s += expr[pos];
                        pos++;
                    }
                    koeff *= stol(s);
                    pos--;
                    break;
                }
            }
        }
        NM[make_pair(stN, stM)] += koeff;
        string toPrint;
        for (auto &it : NM) {
            long val = it.second;
            long j = it.first.first;
            long k = it.first.second;
            if (val != 0) {
                if (val == -1) {
                    if (j == 0 && k == 0) {
                        toPrint += "-1";
                    } else {
                        toPrint += '-';
                    }
                } else if (val == 1) {
                    if (toPrint.length() == 0)
                        toPrint += "1";
                    else {
                        toPrint += "+";
                    }
                } else if (val > 0) {
                    if (toPrint.length() != 0)
                        toPrint += "+";
                    toPrint += to_string(val);
                } else {
                    toPrint += to_string(val);
                }
                if (j != 0) {
                    if (j == 1) {
                        toPrint += "n";
                    } else {
                        toPrint += "n^";
                        toPrint += to_string(j);
                    }
                }
                if (k != 0) {
                    if (k == 1) {
                        toPrint += "m";
                    } else {
                        toPrint += "m^";
                        toPrint += to_string(k);
                    }
                }
            }
        }
        if (toPrint.length() == 0) cout << "0" << endl;
        else cout << toPrint << endl;
    }
    return 0;
}