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  1.  
  2. #include <stdio.h>
  3. #include <stdlib.h>
  4. #include <string.h>
  5.  
  6. struct Node {
  7.     char *value;
  8.     struct Node *prev;
  9.     struct Node *next;
  10. };
  11.  
  12. // allocate node with 10-char buffer
  13. struct Node* createNode(const char *value)
  14. {
  15.     struct Node *newNode = malloc(sizeof(struct Node));
  16.  
  17.     newNode->value = malloc(10); 
  18.     strncpy(newNode->value, value, 9);
  19.     newNode->value[9] = '\0';      // safety null termination
  20.     newNode->prev = NULL;
  21.     newNode->next = NULL;
  22.     return newNode;
  23. }
  24.  
  25. // print list
  26. void printList(struct Node *head)
  27. {
  28.     struct Node *curr = head;
  29.  
  30.     printf("NULL <-> ");
  31.     while (curr)
  32.     {
  33.         printf("%s <-> ", curr->value);
  34.         curr = curr->next;
  35.     }
  36.     printf("NULL\n");
  37. }
  38. ////////////////////////////////////////////////////
  39. // insert at end
  40. void pushBack(struct Node **head, const char *value)
  41. {
  42.     struct Node *n = createNode(value);
  43.  
  44.     if (*head == NULL)
  45.     {
  46.         *head = n;
  47.         return;
  48.     }
  49.  
  50.     struct Node *curr = *head;
  51.     while (curr->next)
  52.         curr = curr->next;
  53.  
  54.     curr->next = n;
  55.     n->prev = curr;
  56. }
  57. ////////////////////////////////////////////////////////
  58. // insert after
  59. void insertAfter(struct Node **head, const char *target, const char *value)
  60. {
  61.     struct Node *curr = *head;
  62.  
  63.     while (curr)
  64.     {
  65.         if (strcmp(curr->value, target) == 0)
  66.         {
  67.             struct Node *n = createNode(value);
  68.  
  69.             n->next = curr->next;
  70.             n->prev = curr;
  71.  
  72.             if (curr->next)
  73.                 curr->next->prev = n;
  74.  
  75.             curr->next = n;
  76.             return;
  77.         }
  78.         curr = curr->next;
  79.     }
  80. }
  81. /////////////////////////////////////////////////////////
  82. // insert before
  83. void insertBefore(struct Node **head, const char *target, const char *value)
  84. {
  85.     struct Node *curr = *head;
  86.  
  87.     while (curr)
  88.     {
  89.         if (strcmp(curr->value, target) == 0)
  90.         {
  91.             struct Node *n = createNode(value);
  92.  
  93.             n->next = curr;
  94.             n->prev = curr->prev;
  95.  
  96.             if (curr->prev)
  97.                 curr->prev->next = n;
  98.             else
  99.                 *head = n;
  100.  
  101.             curr->prev = n;
  102.             return;
  103.         }
  104.         curr = curr->next;
  105.     }
  106. }
  107.  
  108. // delete after
  109. void deleteAfter(struct Node **head, const char *target)
  110. {
  111.     struct Node *curr = *head;
  112.  
  113.     while (curr)
  114.     {
  115.         if (strcmp(curr->value, target) == 0 && curr->next)
  116.         {
  117.             struct Node *del = curr->next;
  118.  
  119.             curr->next = del->next;
  120.             if (del->next)
  121.                 del->next->prev = curr;
  122.  
  123.             free(del->value);  // FREE STRING
  124.             free(del);         // FREE NODE
  125.             return;
  126.         }
  127.         curr = curr->next;
  128.     }
  129. }
  130.  
  131. // delete before
  132. void deleteBefore(struct Node **head, const char *target)
  133. {
  134.     struct Node *curr = *head;
  135.  
  136.     while (curr)
  137.     {
  138.         if (strcmp(curr->value, target) == 0 && curr->prev)
  139.         {
  140.             struct Node *del = curr->prev;
  141.  
  142.             if (del->prev)
  143.             {
  144.                 del->prev->next = curr;
  145.                 curr->prev = del->prev;
  146.             }
  147.             else
  148.             {
  149.                 *head = curr;
  150.                 curr->prev = NULL;
  151.             }
  152.  
  153.             free(del->value);  // FREE STRING
  154.             free(del);         // FREE NODE
  155.             return;
  156.         }
  157.         curr = curr->next;
  158.     }
  159. }
  160.  
  161. // reverse list
  162. void reverseList(struct Node **head)
  163. {
  164.     struct Node *curr = *head;
  165.     struct Node *temp = NULL;
  166.  
  167.     while (curr)
  168.     {
  169.         temp = curr->prev;
  170.         curr->prev = curr->next;
  171.         curr->next = temp;
  172.         curr = curr->prev;
  173.     }
  174.  
  175.     if (temp)
  176.         *head = temp->prev;
  177. }
  178.  
  179. // FREE ENTIRE LIST (IMPORTANT)
  180. void freeList(struct Node **head)
  181. {
  182.     struct Node *curr = *head;
  183.     struct Node *next = NULL;
  184.  
  185.     while (curr)
  186.     {
  187.         next = curr->next;
  188.         free(curr->value);
  189.         free(curr);
  190.         curr = next;
  191.     }
  192.  
  193.     *head = NULL;
  194. }
  195.  
  196. // demo
  197. int main()
  198. {
  199.     struct Node *head = NULL;
  200.  
  201.     pushBack(&head, "A");
  202.     pushBack(&head, "B");
  203.     pushBack(&head, "C");
  204.     pushBack(&head, "D");
  205.  
  206.     printList(head);
  207.  
  208.     insertAfter(&head, "B", "X");
  209.     printList(head);
  210.  
  211.     insertBefore(&head, "C", "Y");
  212.     printList(head);
  213.  
  214.     deleteAfter(&head, "A");
  215.     printList(head);
  216.  
  217.     deleteBefore(&head, "D");
  218.     printList(head);
  219.  
  220.     reverseList(&head);
  221.     printList(head);
  222.  
  223.     freeList(&head);   // CLEAN MEMORY
  224.  
  225.     return 0;
  226. }
Success #stdin #stdout 0s 5320KB
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stdin
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Standard input is empty
stdout
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NULL <-> A <-> B <-> C <-> D <-> NULL
NULL <-> A <-> B <-> X <-> C <-> D <-> NULL
NULL <-> A <-> B <-> X <-> Y <-> C <-> D <-> NULL
NULL <-> A <-> X <-> Y <-> C <-> D <-> NULL
NULL <-> A <-> X <-> Y <-> D <-> NULL
NULL <-> D <-> Y <-> X <-> A <-> NULL
https://ideone.com/swjzci
language:
C (gcc 8.3)
created:
4 hours ago
visibility:
public

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