P1024 一元三次方程求解

P1024 一元三次方程求解

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#include<cstdio>
#include<iostream>
#include<algorithm>
using namespace std;
double a,b,c,d;
double f(double data)
{
	return a*data*data*data+b*data*data+c*data+d;
}
void bit_sreach(double l,double r)
{
	while(l+0.001<r)
	{
		double mid=(l+r)/2;
		if(f(mid)==0.0)//一个坑点
		{
			printf("%.2lf",mid);
			break;
		}
		if(f(mid)*f(l)<0)
			r=mid;
		if(f(mid)*f(r)<0)
			l=mid;
	}
	printf("%.2lf ",l);
}
int main()
{
	scanf("%lf%lf%lf%lf",&a,&b,&c,&d);
	for(double i=-100;i<=100;i++)
	{
		if(f(i)==0.0)//注意
		{
			printf("%.2lf ",i);
		}
		if(f(double(i))*f(double(i+1))<0)
			bit_sreach(i,i+1);
	}
	return 0;
}