c++实现复数相加

#include <iostream>
#include <cmath>
using namespace std;
class fs{
    public:
    int x = 0, y = 0;
    fs(){}
    fs(string s){
        int m = 0, flag = 1, k = s.size();
        for(int i = 0; i < k; i++)
        {
            if(s[i] == '-') x = m * flag, flag = -1, m = 0;
            else if(s[i] == '+') x = m * flag, flag = 1, m = 0;
            else if(s[i] >= '0' && s[i] <= '9') m = m * 10 + s[i] - '0';
            else if(s[i] == 'i'){
                if(m == 0) y = flag;
                else y = m * flag;
            }
        }
        if(y == 0) x = m * flag;
    }
    void display(){
        if(x != 0){
            cout << x;
            if(y != 0){
                if(y > 0) cout << '+';
                if(abs(y) != 1) cout << y;
                else if(y == -1) cout << '-';
                cout << 'i';
            }
        }
        else{
            if(y != 0){
                if(y == -1) cout << '-';
                else if(y == 1) ;
                else cout << y;
                cout << 'i';
            }
            else cout << 0;
        }
    }
    fs operator +(fs &a){
        a.x += x, a.y += y;
        return a;
    }
};
int main()
{
    string s;
    fs a;
    while(1){
        cin >> s;
        if(s == "0") break;
        fs b(s);
        a = a + b;
    }
    a.display();
    return 0;
}