#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <string.h>
#include "numbers.h"
#include "bintree.h"

// --- Hilfsfunktion: Vergleich von unsigned int ------------------
static int compareUInt(const void *a, const void *b)
{
    unsigned int ua = *(const unsigned int *)a;
    unsigned int ub = *(const unsigned int *)b;

    if (ua < ub) return -1;
    if (ua > ub) return 1;
    return 0;
}

// Returns len random numbers between 1 and 2x len in random order which are all different,
// except for two entries. Uses the binary search tree to avoid duplicates.
unsigned int *createNumbers(unsigned int len)
{
    if (len < 2)
        return NULL;

    unsigned int *arr = malloc(sizeof(unsigned int) * len);
    if (!arr)
        return NULL;

    srand((unsigned int)time(NULL));

    TreeNode *root = NULL;

    unsigned int count = 0;
    while (count < len - 1)      // generate len-1 UNIQUE numbers
    {
        unsigned int val = (rand() % (2 * len)) + 1;

        int isDup = 0;
        root = addToTree(root, &val, sizeof(unsigned int), compareUInt, &isDup);

        if (!isDup)
        {
            arr[count++] = val;
        }
    }

    // pick a random existing value to duplicate
    unsigned int duplicateIndex = rand() % (len - 1);
    arr[len - 1] = arr[duplicateIndex];

    clearTree(root);
    return arr;
}

// Returns the only number in the array that occurs twice.
unsigned int getDuplicate(const unsigned int numbers[], unsigned int len)
{
    if (!numbers || len < 2)
        return 0;

    // copy array
    unsigned int *copy = malloc(sizeof(unsigned int) * len);
    if (!copy)
        return 0;

    memcpy(copy, numbers, sizeof(unsigned int) * len);

    // sort
    for (unsigned int i = 0; i < len - 1; i++)
    {
        for (unsigned int j = i + 1; j < len; j++)
        {
            if (copy[j] < copy[i])
            {
                unsigned int t = copy[i];
                copy[i] = copy[j];
                copy[j] = t;
            }
        }
    }

    // find adjacent duplicate
    unsigned int duplicate = 0;
    for (unsigned int i = 0; i < len - 1; i++)
    {
        if (copy[i] == copy[i + 1])
        {
            duplicate = copy[i];
            break;
        }
    }

    free(copy);
    return duplicate;
}