题解

#include <bits/stdc++.h>
using namespace std;
double a, b, c, d;
double check(double x) {
	return a * x * x * x + b * x * x + c * x + d;
}
int main() {
	cin >> a >> b >> c >> d;
	for (double i = -100; i < 100; i++) {
		double j = i + 1;
		if (check(i) == 0)
   			cout<<fixed<<setprecision(2)<<i<<" ";
		if (check(j)*check(i) < 0) {
			double l = i;
			double r = j;
			while (r - l > 0.00001) {
				double mid = (l + r) / 2.0;
				if (check(l)*check(mid) < 0)
					r = mid;
				else
					l = mid;
			}
			cout<<fixed<<setprecision(2)<<l<<" ";
		}
	}
	return 0;
}

30行