二次方程计算器

#include <iostream>
#include <cstdio>
#include <string>
#include <cctype>
#include <cmath>
using namespace std;
string str;
int a, b, c, i, flag, f;
int getdigit(char *s) {
    int tmp = 0, j = 0;
    while(isdigit(s[j])) {
        tmp = tmp * 10 + s[j] - '0';
        i++, j++;
    }
    return tmp;
}
void sign() {
    if(str[i] == '+')
        f = 1;
    if(str[i] == '-')
        f = -1;
    if(str[i] == '=')
        flag = -1;
}
void solve() {
    cin >> str;
    int len = str.length();
    flag = 1, f = 1;
    a = b = c = 0;
    for(i = 0; i < len; i++) {
        sign();
        if(str[i] == 'x') {
            if(str[i + 1] == '^') {
                a += f * flag;
                i += 2;
                continue;
            }
            else {
                b += f * flag;
            }
        }
        if(isdigit(str[i])) {
            int tmp = getdigit(&str[i]);
            if(str[i] == 'x') {
                if(str[i + 1] == '^'){
                    a += tmp * f * flag;
                    i += 2;
                }
                else b += tmp * f * flag;
            }
            else {
                c += tmp * f * flag;
                sign();
            }
        }
    }
    int delta = b * b - 4 * a * c;
    if(delta < 0) printf("No Resolution\n");
    else {
        double x1 = - b / (2.0 * a) - sqrt(1.0 * delta) / (2.0 * a), x2 = - b / (2.0 * a) + sqrt(1.0 * delta) / (2.0 * a);
        printf("%.2f %.2f\n", x1, x2);
    }
}
int main() {
    solve();
    return 0;
}