Find the common ancestor of any two numbers in a binary tree

The code is as follows ：

void  Anales(int arr[],int p, int q)

{

    int pos = -1;

    int size = 0;

    int as[1] = { 0 };

    int indexP = 0;

    int indexQ = 0;

    while (arr[size] != as[1])

    {

        if (arr[size] == p)

        {

            indexP = size;

        }

        if (arr[size] == q)

        {

            indexQ = size;

        }

        size++;

    }

    if (indexP > indexQ)

    {

        int subInt = indexP - indexQ; // For example, the interval between indexes is exactly equal to the smaller index , So their male // The common ancestor index is 0

        if (subInt == indexQ)

        {

            pos = 0;

        }

        else 

        {

            int fatherP = indexP;

            while (fatherP > indexQ)

            {

                if (fatherP % 2) // If the current index is even , Its upper level = ( Current index - 2)/2

                {

                    fatherP = (fatherP - 2) / 2;

                }

                else // If the current index is odd , Its upper level = ( Current index - 1)/2

                {

                    fatherP = (fatherP - 1) / 2;

                }

            }

            if (fatherP == indexQ) 

            {

                pos = fatherP;

            }

            else 

            {

                // At the same time, look for superiors until they are equal   

                while (fatherP != indexQ) 

                {

                    if (fatherP % 2)

                    {

                        fatherP = (fatherP - 2) / 2;

                    }

                    else 

                    {

                        fatherP = (fatherP - 1) / 2;

                    }

                    if (indexQ % 2)

                    {

                        indexQ = (indexQ - 2) / 2;

                    }

                    else 

                    {

                        indexQ = (indexQ - 1) / 2;

                    }

                }

                pos = indexQ;

            }

    

        }

    }

    else if (indexQ > indexP)

    {

        int subInt = indexQ - indexP;

        if (subInt == indexP)

        {

            pos = 0;

        }

        else

        {

            while (indexQ > indexP)

            {

                if (indexQ % 2)

                {

                    indexQ = (indexQ - 2) / 2;

                }

                else

                {

                    indexQ = (indexQ - 1) / 2;

                }

            }

            if (indexP == indexQ)

            {

                pos = indexQ;

            }

            else

            {

                while (indexP != indexQ)

                {

                    if (indexP % 2)

                    {

                        indexP = (indexP - 2) / 2;

                    }

                    else

                    {

                        indexP = (indexP - 1) / 2;

                    }

                    if (indexQ % 2)

                    {

                        indexQ = (indexQ - 2) / 2;

                    }

                    else

                    {

                        indexQ = (indexQ - 1) / 2;

                    }

                }

                pos = indexQ;

            }

        }

    }

    else 

    {

        pos = indexP;

    }

    

    std::cout << " Common ancestor :" << arr[pos] << "\t Indexes :" << pos << std::endl;

}

   

int main()

{

int arr[15] = { 3,5,1,6,2,0,8,0,0,7,4,0,0,0,0 };

    Anales(arr,5,4);

}