c++拉格朗日插值法

#include <cstdlib>
#include <iostream>

using namespace std;
double lagrange(double F,int m,double f[],double g[]);//建立拉格朗日函数 

int main(int argc, char *argv[])
{   int n;
    cout<<"输入样例点的个数n"<<endl;
    cin>>n;  //输入样例点个数
    int i;
    double x[100],y[100];
    for(i=0;i<n;i++)
    {cout<<"输入x"<<i<<"和y"<<i<<endl;
      cin>>x[i]>>y[i];
      }
    double X=0;
    cout<<"输入要计算的X"<<endl;
    cin>>X;
    cout<<"由拉格朗日公式"<<endl;
    cout<<"最终的近似结果Y="<<lagrange(X,n,x,y)<<endl; 
    system("PAUSE");
    return EXIT_SUCCESS;
    
}
    double lagrange(double F,int m,double f[],double g[])
    {int a,b;
     double Y=0,la=0;
     for(b=0;b<m;b++)//完成公式f(Xn)外层嵌套循环f[b]=i
     {double l=1;