Matt Wright Arrays

README.md

@@ -1,3 +1,5 @@
+Matt Wright 3/25/2019
+
 # Arrays
 
 Arrays are the most common and perhaps the simplest data structures. Are they really so simple though? High-level languages like Python, JavaScript, Swift and Java all have built-in "magic" that hides the complexity of many array functions. Although the complexity is hidden, you still have to pay the performance costs of that complexity.
@@ -50,8 +52,3 @@ Resizing involves allocating a block of memory with double the storage, copying
 - `sort()`
 
 Check the official documentation or use Python's `help()` method for implementation details.
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-
-
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-

arrays/arrays.c

@@ -3,13 +3,13 @@
 #include <string.h>
 #include <errno.h>
 
-typedef struct Array {
-  int capacity;  // How many elements can this array hold?
-  int count;  // How many states does the array currently hold?
-  char **elements;  // The string elements contained in the array
+typedef struct Array
+{
+  int capacity;    // How many elements can this array hold?
+  int count;       // How many states does the array currently hold?
+  char **elements; // The string elements contained in the array
 } Array;
 
-
 /************************************
  *
  *   CREATE, DESTROY, RESIZE FUNCTIONS
@@ -19,45 +19,57 @@ typedef struct Array {
 /*****
  * Allocate memory for a new array
  *****/
-Array *create_array (int capacity) {
+Array *create_array(int capacity)
+{
   // Allocate memory for the Array struct
-
+  Array *arr = malloc(sizeof(Array));
   // Set initial values for capacity and count
-
+  arr->capacity = capacity;
+  arr->count = 0;
   // Allocate memory for elements
-
+  arr->elements = malloc(sizeof(char *) * capacity);
+  return arr;
 }
 
-
 /*****
  * Free memory for an array and all of its stored elements
  *****/
-void destroy_array(Array *arr) {
+void destroy_array(Array *arr)
+{
 
   // Free all elements
-
+  if (arr->elements != NULL)
+  {
+    free(arr->elements);
+  }
   // Free array
-
+  free(arr);
 }
 
 /*****
  * Create a new elements array with double capacity and copy elements
  * from old to new
  *****/
-void resize_array(Array *arr) {
+void resize_array(Array *arr)
+{
 
   // Create a new element storage with double capacity
-
+  char **double_storage = malloc(2 * sizeof(arr));
   // Copy elements into the new storage
-
+  for (int i = 0; i < arr->count; i++)
+  {
+    double_storage[i] = arr->elements[i];
+  }
   // Free the old elements array (but NOT the strings they point to)
-
+  if (arr->elements != NULL)
+  {
+    free(arr->elements);
+  }
   // Update the elements and capacity to new values
-
+  arr->elements = double_storage;
+  arr->capacity = 2 * arr->capacity;
 }
 
-
-
 /************************************
  *
  *   ARRAY FUNCTIONS
@@ -69,43 +81,65 @@ void resize_array(Array *arr) {
  *
  * Throw an error if the index is out of range.
  *****/
-char *arr_read(Array *arr, int index) {
-
-  // Throw an error if the index is greater than the current count
+char *arr_read(Array *arr, int index)
+{
 
+  // Throw an error if the index is greater than or equal to the current count
+  if (index >= arr->count)
+  {
+    fprintf(stderr, "Error: index %d greater than the current count.\n", index);
+    return NULL;
+  }
   // Otherwise, return the element at the given index
+  else
+  {
+    return arr->elements[index];
+  }
 }
 
-
 /*****
  * Insert an element to the array at the given index
  *****/
-void arr_insert(Array *arr, char *element, int index) {
+void arr_insert(Array *arr, char *element, int index)
+{
 
   // Throw an error if the index is greater than the current count
-
+  if (index > arr->count)
+  {
+    printf("Error: index greater than the current count.\n");
+  }
   // Resize the array if the number of elements is over capacity
-
+  if (arr->count == arr->capacity)
+  {
+    resize_array(arr);
+  }
   // Move every element after the insert index to the right one position
-
+  for (int i = index; i < arr->count; i++)
+  {
+    arr->elements[i + 1] = arr->elements[i];
+  }
   // Copy the element and add it to the array
-
+  arr->elements[index] = element;
   // Increment count by 1
-
+  arr->count += 1;
 }
 
 /*****
  * Append an element to the end of the array
  *****/
-void arr_append(Array *arr, char *element) {
+void arr_append(Array *arr, char *element)
+{
 
   // Resize the array if the number of elements is over capacity
   // or throw an error if resize isn't implemented yet.
-
+  if (arr->count == arr->capacity)
+  {
+    resize_array(arr);
+  }
   // Copy the element and add it to the end of the array
-
+  arr->elements[arr->count] = element;
   // Increment count by 1
-
+  arr->count += 1;
 }
 
 /*****
@@ -114,33 +148,54 @@ void arr_append(Array *arr, char *element) {
  *
  * Throw an error if the value is not found.
  *****/
-void arr_remove(Array *arr, char *element) {
-
+void arr_remove(Array *arr, char *element)
+{
+  int count = 0;
   // Search for the first occurence of the element and remove it.
+  for (int i = 0; i < arr->count; i++)
+  {
+    if (count != 0)
+    {
+      break;
+    }
+    if (arr->elements[i] == element)
+    {
+      count = i;
+    }
+  }
   // Don't forget to free its memory!
+  if (count)
+  {
+    arr->elements[count] = NULL;
+    free(arr->elements[count]);
+  }
 
   // Shift over every element after the removed element to the left one position
-
+  for (int j = count; j < arr->count; j++)
+  {
+    arr->elements[j] = arr->elements[j + 1];
+  }
   // Decrement count by 1
-
+  arr->count--;
 }
 
-
 /*****
  * Utility function to print an array.
  *****/
-void arr_print(Array *arr) {
+void arr_print(Array *arr)
+{
   printf("[");
-  for (int i = 0 ; i < arr->count ; i++) {
+  for (int i = 0; i < arr->count; i++)
+  {
     printf("%s", arr->elements[i]);
-    if (i != arr->count - 1) {
+    if (i != arr->count - 1)
+    {
       printf(",");
     }
   }
   printf("]\n");
 }
 
-
 #ifndef TESTING
 int main(void)
 {