P1024 [NOIP2001 提高组] 一元三次方程求解提交152.96k通过59.08k时间限制1.00s内存限制125.00MB提交答案加入题单

#include  
using namespace std;
typedef double dl;
const dl eps = 1e-3;
dl a, b, c, d;

double f(dl x) {
	return  x * x * x * a + x * x * b + x * c + d ;
}



int main() {
	cin >> a >> b >> c >> d;
	for (double i = -100; i < 100 ; i++) {
		double j = i + 1;

		if (!f(i)) {
			printf("%.2f ", i);
			continue;
		}

		if (f(i) * f(j) < 0) {
			double l = i;
			double r = j;
			while (r - l > eps) {
				dl mid = (l + r) / 2;
				if (f(mid) * f(r) <= 0) {
					l = mid;
				} else {
					r = mid;
				}
			}

			printf("%.2f ", l);


		}
	}


}