Newton and Lagrange interpolation algorithms

#include <stdio.h>
#include <stdlib.h>
#include <iostream.h>
typedef struct DATA
{
float x;
Float y;
Structure of}data;//variable x and function value y
Data d[20];//up to 20 sets
float f (int s,int t)//Newton interpolation to return to the plug-in
{
if (t==s+1)
Return (D[T].Y-D[S].Y)/(d[t].x-d[s].x);
Else
Return (f (s+1,t)-F (s,t-1))/(d[t].x-d[s].x);
}
Float Newton (float x,int count)
{
int n;
while (1)
{
cout<< "Please input n value (ie n time interpolation):"//Get interpolation times
cin>>n;
if (n<=count-1)//interpolation times must not be greater than count-1 times
Break
Else
System ("CLS");
}
Initialize T,Y,YT.
float t=1.0;
float y=d[0].y;
float yt=0.0;
Calculate Y-Values
for (int j=1;j<=n;j++)
{
t= (x-d[j-1].x) *t;
Yt=f (0,j) *t;
Cout<<f (0,J) <<endl;
Y=y+yt;
}
return y;
}
Float Lagrange (float x,int count)
{
float y=0.0;
for (int k=0;k<count;k++)//Here defaults to count-1 secondary interpolation
{
Float p=1.0;//Initialize P
for (int j=0;j<count;j++)
{//Calculate P's value
if (K==J) continue;//to determine whether the same number
p=p* (x-d[j].x)/(d[k].x-d[j].x);
}
y=y+p*d[k].y;//sum
}
Return y;//returns the value of Y
}
void Main ()
{
float X,y;
int count;
while (1)
{
cout<< "Please enter x[i],y[i] number of groups, no more than 20 groups:";//Require users to enter data group number
cin>>count;
if (count<=20)
break;//Check if the input is legal
System ("CLS");
}
Get each group of data
for (int i=0;i<count;i++)
{
cout<< "Please enter the value of" <<i+1<< "group x:";
cin>>d[i].x;
cout<< "Please enter the value of" <<i+1<< "group y:";
cin>>d[i].y;
System ("CLS");
}
cout<< "Please enter the value of x:";//Get the value of the variable x
cin>>x;
while (1)
{
int choice=3;
cout<< "Please choose which interpolation method to use to calculate:" <<endl;
cout<< "(0): Exit" <<endl;
cout<< "(1): Lagrange" <<endl;
cout<< "(2): Newton" <<endl;
cout<< "Enter your choice:";
cin>>choice;//gets the user's selection
if (choice==2)
{
cout<< "You chose the Newton interpolation calculation method, the result is:";
Y=newton (x,count); break;//call the corresponding handler function
}
if (choice==1)
{
cout<< "You chose the Lagrange interpolation calculation method, the result is:";
Y=lagrange (x,count); break;//call the corresponding handler function
}
if (choice==0)
Break
System ("CLS");
cout<< "INPUT error!!!!" <<endl;
}
cout<<x<< "," <<y<<endl;//output final result
}