test.cpp

输入系数和最高阶次

#include<stdio.h> 
#include<math.h> 
float f(float Coef[],float x) 
{ 
return float(Coef[0]+Coef[1]*x+Coef[2]*pow(x,2)+Coef[3]*pow(x,3)+Coef[4]*pow(x,4)+Coef[5]*pow(x,5)+Coef[6]*pow(x,6)+Coef[7]*pow(x,7)+Coef[8]*pow(x,8)+Coef[9]*pow(x,9)+Coef[10]*pow(x,10)+Coef[11]*pow(x,11)+Coef[12]*pow(x,12)+Coef[13]*pow(x,13)+Coef[14]*pow(x,14)); 
//返回多项式的值 
} 

void GetCoefficient(float Coef[],int &degree)
{
int a;
printf("please input The degree of the polynomial[3,15]:"); 
scanf("%d",&a); 
fflush(stdin); 
degree=a;
printf("please input the coefficients of a polynomial:\n"); 
for(int i=0;i<=degree;i++)//从低阶到高阶输入系数 
{ 
scanf("%f",&Coef[i]); 
fflush(stdin); 
} 
for(i;i<15;i++)//系数为0的 
{ 
Coef[i]=0.0; 
} 
}

float GetPrecision()
{
float a;
printf("please input Precision:\n"); 
scanf("%d",&a);
fflush(stdin); 
return a;
}

void SetInitialInterval(float Coef[],int degree,float &xlow,float &xup)
{
float a,b;
printf("please input xlow:\n"); 
scanf("%f",&a);
fflush(stdin); 
xlow=a;
printf("please input xup:\n"); 
scanf("%f",&b);
fflush(stdin); 
xup=b;
}

float ApproximateRoot(float Coef[],int degree,float epsilon,float xlow,float xup)
{
float xres=(xlow+xup)/2; 
while(fabs(f(Coef,xres))>epsilon)//二分法求根 
{ 
if(f(Coef,xres)*f(Coef,xup)<0) 
xlow=xres; 
else 
xup=xres; 
xres=(xlow+xup)/2; 
} 
return xres;
}

void main() //主函数
{ 
float Coef[15];
int degree;
float epsilon;
float xres, xlow, xup;
GetCoefficient(Coef,degree);
epsilon=GetPrecision();
SetInitialInterval(Coef,degree,xlow,xup);
xres=ApproximateRoot(Coef,degree,epsilon,xlow,xup);
printf("the result is : %f",xres);
}