#include <stdio.h>
#include <iostream.h>
#include <conio.h>

using namespace std;

int main()
{ bool menu=true;
     while (menu)
    {
        cout<<"1: \n";
        cout<<"2: \n";
        cout<<"3: \n";
        cout<<"4: \n";
        cout<<"5: \n";
     switch (getchar())
        {
            case '1':menu=false; break;

        }

    }
    cout<<"Bay! Bay! \n";

   return 0;
}

#include <stdio.h>
#include <iostream.h>
#include <conio.h>
int main()
{ bool menu=true;
    char ch;
   while (menu)
    {
        cout<<"1: \n";
        cout<<"2: \n";
        cout<<"3: \n";
        cout<<"4: \n";
        cout<<"5: \n";
         cin>>ch;
     switch (ch)
        {
            case '1':menu=false; break;

        }

    }
    cout<<"Bay! Bay! \n";

   return 0;
}

cout << endl;

#include <stdio.h>
#include <iostream.h>
#include <conio.h>
#include <stdlib.h>
#include <math.h>
#include <fstream.h>

using namespace std;

int pol_lag(int&, double *mas);

int main()
{   int kol_xy,i=0;
    system("cls");

    cout<<"Vvedite kol-vo znacheniy x && y: ";
    cin>>kol_xy;
    double mas [kol_xy] [3]; // <---Вот этот массив надо передать в   pol_lag(int &kol_xyx, double *mas)

   return 0;
}

int  pol_lag(int &kol_xyx, double *mas)
{

    return 0;
}

int pol_lag(int&, double *mas[3]);

int  pol_lag(int &kol_xyx, double *mas[3])
{
    double p = 1;
    for(int i = 0; i < kol_xyx; i++) {
        p *= mas[i][1]; // это аналог твоего выражения
    }
    return 0;
}

#include <iostream>
#include <fstream>
#include <stdlib.h>

using namespace std;

int  pol_lag(int&, double mas[][3]);

int main()
{
    int  kol_xy,i=0;
    system("cls");

    cout<<"Vvedite kol-vo znacheniy x && y: ";
    cin>>kol_xy;
    double mas [kol_xy] [3];
    ifstream infile("data.txt");

    while (i<kol_xy) {
        infile>>mas [i][0]>>mas [i][1]>>mas [i][2];
        printf("X = %lg; Y = %lg; x = %lg\n", mas [i][0],mas [i][1],mas [i][2] );
        i++;
    }
    cout<<"------------------------------------\n";

    pol_lag(kol_xy, mas);
    getchar();
    cout<<"Good Luck!\n";
    cout<<"Bay! Bay! \n";
    return 0;
}

int  pol_lag(int &kol_xyx, double mas[][3])
{
    for( int xn=0;xn<kol_xyx;xn++) {
        double s=0;
        for(int i=0;i<kol_xyx;i++) {
            double p=1;
            for(int j=0;j<kol_xyx;j++) {
                p *= (i != j) ? ((mas[xn][2] - mas[j][0])/(mas[i][0]-mas[j][0])) : (mas [i][1]);
            }
            s+=p;
        }
        cout<<"Resul for x"<<xn+1<<":  "<<mas[xn][2]<<"  | y:"<<s<<"\n";
    }
    return 0;
}

    cout<<"Vvedite kol-vo znacheniy x && y: ";
    (cin>>kol_xy).get(); // прочитать число и сразу прочесть '\n'

int m; //<---какраз номер метода
(cin>>m).get();

if (m==1) then ifstream infile("data.txt"); else ifstream infile("data1.txt");

 infile.getline(s,255);

    int m;
    (cin>>m).get();

    ifstream infile;
    if(m == 1) {
        infile.open("data.txt");
    }
    else {
        infile.open("data1.txt");
    }

#include <stdio.h>
#include <iostream.h>
#include <stdlib.h>
#include <math.h>
#include <fstream>

using namespace std;

int main()
{   double mas [3][6];char s[255];
    system("cls");

    ifstream infile("slu.txt");
    infile.getline(s,255);
    for (int i=0;i<3;i++)
        {
             infile>>mas [i][0]>>mas [i][1]>>mas [i][2]>>mas [i][3];
            cout<<mas [i][0]<<"  "<<mas [i][1]<<"  "<<mas [i][2]<<"  "<<mas [i][3]<<"\n";
            mas[i][4]=mas [i][3];
        }

    cout<<"------------------------------------\n";
    for(int i=0;i<3;i++)    {  for(int j=0;j<4;j++) mas[i][j]/= (-1*mas[i][i]);

            mas[i][i]=0;
            cout<<mas [i][0]<<"  "<<mas [i][1]<<"  "<<mas [i][2]<<"  "<<mas [i][3]<<"\n";

            };




    getchar();
    cout<<"Good Luck!\n";
    cout<<"Bay! Bay! \n";

   return 0;
}

 begin
writeln(' vot takoi ');
readln;
end.

#include <iostream>
#include <conio.h>

int main()
{ 
   getch();
   return 0;
 }

double func(double &x)
{
  return (9/2);
}

double func(double &x)
{
  return (9./2); // Девятка - уже вещественная
}

double func(double &x)
{
  return ((double)9/2);
}