TestCode

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

typedef struct point
{
    int x; int y;
}POINT;

int noduplicates(POINT *data, POINT input, int count);
int validPair(POINT input);
void display(POINT input);
POINT getpoint();
void domain(POINT *, int *, int count);
void range(POINT *, int *, int count);
int isReflexive(POINT *data, int *domain, int *range, int count); //if each of the combined values of the domain and range have reflexive pairs
int isSymmetric(POINT *, int count); //if each pair has a symmetric pair
int isTransitive(POINT *data, int count);
int isEq(POINT *, int *);


void main()
{
    POINT input[81];
    int index = 0; //base count from the initial index
    int domain[9], range[9];
    char selection;
    do
    {
        printf("\n\n\t\tBeginning values SET={1,2,3,4,5,6,7,8,9}");
        printf("\nPlease enter values for ordered pair #%d (x,y)", index + 1);
        input[index] = getpoint();
        if (!validPair(input[index]))
        {
            printf("\n\nInvalid input. An element of the pair does not exist in the original set. Press any key to continue input.");
            _getch();
            continue;
        }
        if (!noduplicates(input, input[index], index))
        {
            printf("\n\nOrdered pair already exists. Press any key to continue input.");
            _getch();
            continue;
        }
        printf("\n\nDo you want to add more pairs? [Y]es or any other key to continue");
        selection = getchar();
        if ((selection != 'Y') || (selection != 'y')) break;
        index++;
    } while (1);

}

void domain(POINT *input, int *output, int count)
{
    int temp[9] = { 0 };
    for (int i = 0; i < count + 1; i++)
    {
        temp[input[i].x - 1] = input[i].x;
    }
    for (int i = 0; i < count + 1; i++)
    {
        int j = 0;
        if (temp[i])
        {
            output[j] = temp[i];
            j++;
        }
    }
}
void range(POINT *input, int *output, int count)
{
    int temp[9] = { 0 };
    for (int i = 0; i < count + 1; i++)
    {
        temp[input[i].y - 1] = input[i].y;
    }
    for (int i = 0; i < count + 1; i++)
    {
        int j = 0;
        if (temp[i])
        {
            output[j] = temp[i];
            j++;
        }
    }
}

int isReflexive(POINT *data, int *domain, int *range, int count)
{
    int temp[9] = { 0 }, i, j, propertypoints = 0, entrycount = 0;
    for (i = 0; i < 9; i++)
    {
        if (domain[i]) temp[domain[i] - 1] = domain[i];
        if (range[i]) temp[range[i] - 1] = range[i];
    }
    //combines domain and range into a single array with no duplicates, blanks are 0.
    for (i = 0; i < 9; i++)
    {
        //if the array cell has content other than 0
        if (temp[i])
            //add to the count of possible reflex pairs
            entrycount++;
            //compare with the points if a reflex pair exists
            for (j = 0; j < count + 1; j++)
                //if a pair (temp[i],temp[i]) exists add a point to the property
                if (data[j].x == temp[i] && data[j].y == temp[i])
                {
                    entrycount++;
                    break;
                }
    }
    if (propertypoints == entrycount) return 1;
    else return 0;
}

int isSymmetric(POINT *data, int count)
{
    int i, j, propertypoints=0;
    for (i = 0; i < count + 1; i++)
    {
        for (j = 0; j < count + 1; j++)
            if ((data[i].x == data[j].y) && (data[i].y == data[j].x)) propertypoints++;
    }
    if (propertypoints == count + 1) return 1;
    else return 0;
}
int isTransitive(POINT *data, int count)
{
    int a, b, c, propertypoints = 0;
    for (a = 0; a < count + 1; a++)
        for (b = 0; b < count + 1; b++)
            for (c = 0; c < count + 1; c++)
                if (data[a].y == data[b].x)
                    if (((data[a].x == data[c].x) && (data[a].y == data[c].y)) || ((data[b].x == data[c].x) && (data[a].y == data[c].y)))
                        propertypoints++;

    if
}

int isEq(POINT *input, int *size)
{
}

POINT getpoint()
{
    POINT input;
    printf("\nX = ");  scanf_s("%d", &input.x);
    printf("\nY = ");  scanf_s("%d", &input.y);
    return input;
}

void display(POINT input)
{
    printf("(%d,%d)", input.x, input.y);
}

int validPair(POINT input)
{
    int control = 0;
    for (int i = 1; i <= 9; i++)
    {
        if (input.x == i) control++;
        if (input.y == i) control++;
        if (control == 2) break;
    }
    if (control == 2) return 1;
    else return 0;
}

int noduplicates(POINT *data, POINT input, int count)
{
    for (int i = 0; i < count + 1; i++)
        if ((input.x == data[i].x) && (input.y == data[i].y)) return 1;
        else return 0;
}