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| 1 | +/** |
| 2 | + * @file |
| 3 | + * |
| 4 | + * @details |
| 5 | + * Circular [Doubly Linked |
| 6 | + * List](https://en.wikipedia.org/wiki/Doubly_linked_list) combines the |
| 7 | + * properties of a doubly linked list and a circular linked list in which two |
| 8 | + * consecutive elements are linked or connected by the previous. Next, the |
| 9 | + * pointer and the last node point to the first node via the next pointer, and |
| 10 | + * the first node points to the last node via the previous pointer. |
| 11 | + * |
| 12 | + * In this implementation, functions to insert at the head, insert at the last |
| 13 | + * index, delete the first node, delete the last node, display list, and get |
| 14 | + * list size functions are coded. |
| 15 | + * |
| 16 | + * @author [Sahil Kandhare](https://github.com/SahilK-027) |
| 17 | + * |
| 18 | + */ |
| 19 | + |
| 20 | +#include <assert.h> /// to verify assumptions made by the program and print a diagnostic message if this assumption is false. |
| 21 | +#include <inttypes.h> /// to provide a set of integer types with universally consistent definitions that are operating system-independent |
| 22 | +#include <stdio.h> /// for IO operations |
| 23 | +#include <stdlib.h> /// for including functions involving memory allocation such as `malloc` |
| 24 | + |
| 25 | +/** |
| 26 | + * @brief Circular Doubly linked list struct |
| 27 | + */ |
| 28 | +typedef struct node |
| 29 | +{ |
| 30 | + struct node *prev, *next; ///< List pointers |
| 31 | + uint64_t value; ///< Data stored on each node |
| 32 | +} ListNode; |
| 33 | + |
| 34 | +/** |
| 35 | + * @brief Create a list node |
| 36 | + * @param data the data that the node initialises with |
| 37 | + * @return ListNode* pointer to the newly created list node |
| 38 | + */ |
| 39 | +ListNode *create_node(uint64_t data) |
| 40 | +{ |
| 41 | + ListNode *new_list = (ListNode *)malloc(sizeof(ListNode)); |
| 42 | + new_list->value = data; |
| 43 | + new_list->next = new_list; |
| 44 | + new_list->prev = new_list; |
| 45 | + return new_list; |
| 46 | +} |
| 47 | + |
| 48 | +/** |
| 49 | + * @brief Insert a node at start of list |
| 50 | + * @param head start pointer of list |
| 51 | + * @param data the data that the node initialises with |
| 52 | + * @return ListNode* pointer to the newly created list node |
| 53 | + * inserted at the head |
| 54 | + */ |
| 55 | +ListNode *insert_at_head(ListNode *head, uint64_t data) |
| 56 | +{ |
| 57 | + if (head == NULL) |
| 58 | + { |
| 59 | + head = create_node(data); |
| 60 | + return head; |
| 61 | + } |
| 62 | + else |
| 63 | + { |
| 64 | + ListNode *temp; |
| 65 | + ListNode *new_node = create_node(data); |
| 66 | + temp = head->prev; |
| 67 | + new_node->next = head; |
| 68 | + head->prev = new_node; |
| 69 | + new_node->prev = temp; |
| 70 | + temp->next = new_node; |
| 71 | + head = new_node; |
| 72 | + return head; |
| 73 | + } |
| 74 | +} |
| 75 | + |
| 76 | +/** |
| 77 | + * @brief Insert a node at end of list |
| 78 | + * |
| 79 | + * @param head start pointer of list |
| 80 | + * @param data the data that the node initialises with |
| 81 | + * @return ListNode* pointer to the newly added list node that was |
| 82 | + * inserted at the head of list. |
| 83 | + */ |
| 84 | +ListNode *insert_at_tail(ListNode *head, uint64_t data) |
| 85 | +{ |
| 86 | + if (head == NULL) |
| 87 | + { |
| 88 | + head = create_node(data); |
| 89 | + return head; |
| 90 | + } |
| 91 | + else |
| 92 | + { |
| 93 | + ListNode *temp1, *temp2; |
| 94 | + ListNode *new_node = create_node(data); |
| 95 | + temp1 = head; |
| 96 | + temp2 = head->prev; |
| 97 | + new_node->prev = temp2; |
| 98 | + new_node->next = temp1; |
| 99 | + temp1->prev = new_node; |
| 100 | + temp2->next = new_node; |
| 101 | + return head; |
| 102 | + } |
| 103 | +} |
| 104 | + |
| 105 | +/** |
| 106 | + * @brief Function for deletion of the first node in list |
| 107 | + * |
| 108 | + * @param head start pointer of list |
| 109 | + * @return ListNode* pointer to the list node after deleting first node |
| 110 | + */ |
| 111 | +ListNode *delete_from_head(ListNode *head) |
| 112 | +{ |
| 113 | + if (head == NULL) |
| 114 | + { |
| 115 | + printf("The list is empty\n"); |
| 116 | + return head; |
| 117 | + } |
| 118 | + ListNode *temp1, *temp2; |
| 119 | + temp1 = head; |
| 120 | + temp2 = temp1->prev; |
| 121 | + if (temp1 == temp2) |
| 122 | + { |
| 123 | + free(temp2); |
| 124 | + head = NULL; |
| 125 | + return head; |
| 126 | + } |
| 127 | + temp2->next = temp1->next; |
| 128 | + (temp1->next)->prev = temp2; |
| 129 | + head = temp1->next; |
| 130 | + free(temp1); |
| 131 | + return head; |
| 132 | +} |
| 133 | + |
| 134 | +/** |
| 135 | + * @brief Function for deletion of the last node in list |
| 136 | + * |
| 137 | + * @param head start pointer of list |
| 138 | + * @return ListNode* pointer to the list node after deleting first node |
| 139 | + */ |
| 140 | +ListNode *delete_from_tail(ListNode *head) |
| 141 | +{ |
| 142 | + if (head == NULL) |
| 143 | + { |
| 144 | + printf("The list is empty\n"); |
| 145 | + return head; |
| 146 | + } |
| 147 | + |
| 148 | + ListNode *temp1, *temp2; |
| 149 | + temp1 = head; |
| 150 | + temp2 = temp1->prev; |
| 151 | + if (temp1 == temp2) |
| 152 | + { |
| 153 | + free(temp2); |
| 154 | + head = NULL; |
| 155 | + return head; |
| 156 | + } |
| 157 | + (temp2->prev)->next = temp1; |
| 158 | + temp1->prev = temp2->prev; |
| 159 | + free(temp2); |
| 160 | + return head; |
| 161 | +} |
| 162 | + |
| 163 | +/** |
| 164 | + * @brief The function that will return current size of list |
| 165 | + * |
| 166 | + * @param head start pointer of list |
| 167 | + * @return int size of list |
| 168 | + */ |
| 169 | +int getsize(ListNode *head) |
| 170 | +{ |
| 171 | + if (!head) |
| 172 | + { |
| 173 | + return 0; |
| 174 | + } |
| 175 | + int size = 1; |
| 176 | + ListNode *temp = head->next; |
| 177 | + while (temp != head) |
| 178 | + { |
| 179 | + temp = temp->next; |
| 180 | + size++; |
| 181 | + } |
| 182 | + return size; |
| 183 | +} |
| 184 | + |
| 185 | +/** |
| 186 | + * @brief Display list function |
| 187 | + * @param head start pointer of list |
| 188 | + * @returns void |
| 189 | + */ |
| 190 | + |
| 191 | +void display_list(ListNode *head) |
| 192 | +{ |
| 193 | + printf("\nContents of your linked list: "); |
| 194 | + ListNode *temp; |
| 195 | + temp = head; |
| 196 | + if (head != NULL) |
| 197 | + { |
| 198 | + while (temp->next != head) |
| 199 | + { |
| 200 | + printf("%" PRIu64 " <-> ", temp->value); |
| 201 | + temp = temp->next; |
| 202 | + } |
| 203 | + if (temp->next == head) |
| 204 | + { |
| 205 | + printf("%" PRIu64, temp->value); |
| 206 | + } |
| 207 | + } |
| 208 | + else |
| 209 | + { |
| 210 | + printf("The list is empty"); |
| 211 | + } |
| 212 | + printf("\n"); |
| 213 | +} |
| 214 | + |
| 215 | +/** |
| 216 | + * @brief access the list by index |
| 217 | + * @param list pointer to the target list |
| 218 | + * @param index access location |
| 219 | + * @returns the value at the specified index, |
| 220 | + * wrapping around if the index is larger than the size of the target |
| 221 | + * list |
| 222 | + */ |
| 223 | +uint64_t get(ListNode *list, const int index) |
| 224 | +{ |
| 225 | + if (list == NULL || index < 0) |
| 226 | + { |
| 227 | + exit(EXIT_FAILURE); |
| 228 | + } |
| 229 | + ListNode *temp = list; |
| 230 | + for (int i = 0; i < index; ++i) |
| 231 | + { |
| 232 | + temp = temp->next; |
| 233 | + } |
| 234 | + return temp->value; |
| 235 | +} |
| 236 | + |
| 237 | +/** |
| 238 | + * @brief Self-test implementations |
| 239 | + * @returns void |
| 240 | + */ |
| 241 | +static void test() |
| 242 | +{ |
| 243 | + ListNode *testList = NULL; |
| 244 | + unsigned int array[] = {2, 3, 4, 5, 6}; |
| 245 | + |
| 246 | + assert(getsize(testList) == 0); |
| 247 | + |
| 248 | + printf("Testing inserting elements:\n"); |
| 249 | + for (int i = 0; i < 5; ++i) |
| 250 | + { |
| 251 | + display_list(testList); |
| 252 | + testList = insert_at_head(testList, array[i]); |
| 253 | + assert(testList->value == array[i]); |
| 254 | + assert(getsize(testList) == i + 1); |
| 255 | + } |
| 256 | + |
| 257 | + printf("\nTesting removing elements:\n"); |
| 258 | + for (int i = 4; i > -1; --i) |
| 259 | + { |
| 260 | + display_list(testList); |
| 261 | + assert(testList->value == array[i]); |
| 262 | + testList = delete_from_head(testList); |
| 263 | + assert(getsize(testList) == i); |
| 264 | + } |
| 265 | + |
| 266 | + printf("\nTesting inserting at tail:\n"); |
| 267 | + for (int i = 0; i < 5; ++i) |
| 268 | + { |
| 269 | + display_list(testList); |
| 270 | + testList = insert_at_tail(testList, array[i]); |
| 271 | + assert(get(testList, i) == array[i]); |
| 272 | + assert(getsize(testList) == i + 1); |
| 273 | + } |
| 274 | + |
| 275 | + printf("\nTesting removing from tail:\n"); |
| 276 | + for (int i = 4; i > -1; --i) |
| 277 | + { |
| 278 | + display_list(testList); |
| 279 | + testList = delete_from_tail(testList); |
| 280 | + assert(getsize(testList) == i); |
| 281 | + // If list is not empty, assert that accessing the just removed element |
| 282 | + // will wrap around to the list head |
| 283 | + if (testList != NULL) |
| 284 | + { |
| 285 | + assert(get(testList, i) == testList->value); |
| 286 | + } |
| 287 | + else |
| 288 | + { |
| 289 | + // If the list is empty, assert that the elements were removed after |
| 290 | + // the correct number of iterations |
| 291 | + assert(i == 0); |
| 292 | + } |
| 293 | + } |
| 294 | +} |
| 295 | + |
| 296 | +/** |
| 297 | + * @brief Main function |
| 298 | + * @returns 0 on exit |
| 299 | + */ |
| 300 | +int main() |
| 301 | +{ |
| 302 | + test(); // run self-test implementations |
| 303 | + return 0; |
| 304 | +} |
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