代码：
#include <iostream>
#include <math.h>
using namespace std;
double x[4]={0.56160,0.56280,0.56401,0.56521};
double y[4]={0.82741,0.82639,0.82577,0.82495};
double f1[3];
double f2[2];
double f3;
double n1()
{
int i;
for(i=1;i<4;i++)
{
f1[i]=(y[i+1]-y[i])/(x[i+1]-x[i]);
cout<<f1[i]<<endl;

}
return(0);
}
double n2()
{
int i;
for(i=1;i<3;i++)
{
f2[i]=(f1[i+1]-f1[i])/(x[i+1]-x[i]);
cout<<f2[i]<<endl;

}
return(0);
}
double n3()
{
f3=(f2[2]-f2[1])/(x[2]-x[1]);
cout<<f3<<endl;
return(0);
}
double N(double x)
{
n1();
n2();
n3();
double N;
N=y[1]
+f1[1]*(x-x[1])
+f2[1]*(x-x[1])*(x-x[2])
+f3*(x-x[1])*(x-x[2])*(x-x[3]);
cout<<N<<endl;
return 0;
}
main()
{
double x;
cin>>x;
N(x);
return 0;
}
有六个相同的错误：E:\C++\Newton插值\newton.cpp(44) : error C2109: subscript requires array or pointer type
谢谢了！！

数组下标越界.
f1[3];
for(i=1;i<4;i++)
{
f1[i]=(y[i+1]-y[i])/(x[i+1]-x[i]);
cout<<f1[i]<<endl;

}
f2[2]同.

数组下标如楼上所述,应该是0到n-1

#include <iostream>
using namespace std;
double x[4]={0.56160,0.56280,0.56401,0.56521};
double y[4]={0.82741,0.82639,0.82577,0.82495};
double f1[3];
double f2[2];
double f3;
//以上定义均为全局变量
double n1()
{
    int i;
for(i=0;i<3;i++)
{
    f1[i]=(y[i+1]-y[i])/(x[i+1]-x[i]);
    cout<<f1[i]<<endl;
    
}
return(0);
}
double n2()
{ 
    int i;
    for(i=0;i<2;i++)
    {
      f2[i]=(f1[i+1]-f1[i])/(x[i+1]-x[i]);
      cout<<f2[i]<<endl;
  
    }
    return(0);
}
double n3()
{
    f3=(f2[2]-f2[1])/(x[2]-x[1]);
    cout<<f3<<endl;
    return(0);
}
double N(double t)        //函数中使用了全局变量,因此不要让局部变量与全局变量同名
{
    n1();
    n2();
    n3();
    double N;
    N=y[1]
        +f1[1]*(t-x[1])
        +f2[1]*(t-x[1])*(t-x[2])
        +f3*(t-x[1])*(t-x[2])*(t-x[3]);
    cout<<N<<endl;
    return 0;
}
int main()                //C++必须明确写出类型名
{
    double x;
    cin>>x;
    N(x);
    return 0;
}