diff --git a/numbers.c b/numbers.c
index 694c6e7..7eac651 100644
--- a/numbers.c
+++ b/numbers.c
@@ -24,7 +24,7 @@ CompareFctType compareFct(const void *arg1, const void *arg2)
 // Returns len random numbers between 1 and 2x len in random order which are all different, except for two entries.
 // Returns NULL on errors. Use your implementation of the binary search tree to check for possible duplicates while
 // creating random numbers.
-unsigned int* createNumbers(unsigned int len)
+unsigned int *createNumbers(unsigned int len)
 {
   srand(time(NULL));
 
@@ -32,7 +32,7 @@ unsigned int* createNumbers(unsigned int len)
 
   int isDuplicate = 0;
   unsigned int number = rand() % (2 * len) + 1;
-  unsigned int* array = malloc(len*sizeof(int));
+  unsigned int *array = malloc(len * sizeof(int));
 
   numbers = addToTree(NULL, &number, sizeof(int), compareFct, &isDuplicate);
   array[0] = number;
@@ -44,7 +44,9 @@ unsigned int* createNumbers(unsigned int len)
     {
       isDuplicate = 0;
       i--;
-    }else{
+    }
+    else
+    {
       array[i] = number;
     }
   }
@@ -54,7 +56,8 @@ unsigned int* createNumbers(unsigned int len)
   int duplicatePosition1 = rand() % len;
   int duplicatePosition2 = rand() % len;
 
-  while(duplicatePosition2 == duplicatePosition1){
+  while (duplicatePosition2 == duplicatePosition1)
+  {
     duplicatePosition2 = rand() % len;
   }
 
@@ -66,11 +69,19 @@ unsigned int* createNumbers(unsigned int len)
 // Returns only the only number in numbers which is present twice. Returns zero on errors.
 unsigned int getDuplicate(const unsigned int numbers[], unsigned int len)
 {
-  qsort(numbers, len, sizeof(int), compareFct);
+  unsigned int *copyNumbers = malloc(sizeof(int) * len);
+  for (int i = 0; i < len; i++)
+  {
+    copyNumbers[i] = numbers [i];
+  }
 
-  for(int i = 0; i < len-1; i++){
-    if(numbers[i] == numbers[i+1]){
-      return numbers[i];
+  qsort(copyNumbers, len, sizeof(int), compareFct);
+
+  for (int i = 0; i < len - 1; i++)
+  {
+    if (copyNumbers[i] == copyNumbers[i + 1])
+    {
+      return copyNumbers[i];
     }
   }