////main.c

#include <stdio.h>

#include "func.h"

int main(void)
{
    int rezult;
    char fname1[256];
    char fname2[256];

    printf("Please, enter first file name: ");
    scanf("%255s", fname1);

    printf("Please, enter second file name: ");
    scanf("%255s", fname2);

    rezult = func(fname1, fname2);

    if (rezult == 1) {
        printf("Yes\n");
    }
    else if (rezult == 0) {
        printf("No\n");
    }
    else {
        printf("Error\n");
    }

    switch (rezult)
    {
    case -6:
        printf("Second sequence is bigger, then first!\n");

        break;
    case -5:
        printf("First sequence is bigger, then second!\n");

        break;
    case -4:
        printf("There is not enough elements!\n");

        break;
    case -3:
        printf("Sequence is empty!\n");

        break;
    case -2:
        printf("Error in reading from file!\n");

        break;
    case -1:
        printf("Can't open file!\n");

        break;
    case 0:
        printf("No, it is not so.\n");

        break;
    case 1:
        printf("Yes, it is so.\n");

        break;
    }

    return 0;
}


//// func.c

#include <stdio.h>
#include <math.h>

#include "func.h"

int func(char* fname1, char* fname2)
{
    int flag;
    double tmp1_1;
    double tmp1_2;
    double tmp1_3;
    double tmp2_1;
    double tmp2_2;
    double tmp2_3;
    FILE* fin1;
    FILE* fin2;

    fin1 = fopen(fname1, "r");

    if (!fin1)
        return -1;

    fin2 = fopen(fname2, "r");

    if (!fin2)
    {
        fclose(fin1);

        return -1;
    }

    if (fscanf(fin1, "%lf", &tmp1_1) != 1)
    {
        if (!feof(fin1))
        {
            fclose(fin1);
            fclose(fin2);

            return -2;
        }
        else
        {
            fclose(fin1);
            fclose(fin2);

            return -3;
        }
    }

    if (fscanf(fin2, "%lf", &tmp2_1) != 1)
    {
        if (!feof(fin2))
        {
            fclose(fin1);
            fclose(fin2);

            return -2;
        }
        else
        {
            fclose(fin1);
            fclose(fin2);

            return -3;
        }
    }

    if (fscanf(fin1, "%lf", &tmp1_2) != 1)
    {
        if (!feof(fin1))
        {
            fclose(fin1);
            fclose(fin2);

            return -2;
        }
        else
        {
            fclose(fin1);
            fclose(fin2);

            return -4;
        }
    }

    if (fscanf(fin2, "%lf", &tmp2_2) != 1)
    {
        if (!feof(fin2))
        {
            fclose(fin1);
            fclose(fin2);

            return -2;
        }
        else
        {
            fclose(fin1);
            fclose(fin2);

            return -4;
        }
    }

    flag = 0;

    while (1)
    {
        if (fscanf(fin1, "%lf", &tmp1_3) != 1)
        {
            if (!feof(fin1))
            {
                fclose(fin1);
                fclose(fin2);

                return -2;
            }
            else if (fscanf(fin2, "%lf", &tmp2_3) != 1)
            {
                if (!feof(fin2))
                {
                    fclose(fin1);
                    fclose(fin2);

                    return -2;
                }
                else
                {
                    fclose(fin1);
                    fclose(fin2);

                    if (flag == 0)
                        return -4;
                    else
                        return 1;
                }
            }
            else
            {
                fclose(fin1);
                fclose(fin2);

                return -6;
            }

        }

        if (fscanf(fin2, "%lf", &tmp2_3) != 1)
        {
            if (!feof(fin2))
            {
                fclose(fin1);
                fclose(fin2);

                return -2;
            }
            else
            {
                fclose(fin1);
                fclose(fin2);

                return -5;
            }
        }

        if (fabs(tmp2_2 - 0.5 * (tmp1_1 + tmp1_3)) > 1e-100)
        {
            fclose(fin1);
            fclose(fin2);

            return 0;
        }
        else
            flag = 1;

        tmp1_1 = tmp1_2;
        tmp1_2 = tmp1_3;

        tmp2_1 = tmp2_2;
        tmp2_2 = tmp2_3;
    }
}



////func.h

int func(char* fname1, char* fname2);