P1024 一元三次方程求解

P1024 一元三次方程求解

---

#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;
}