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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <ctype.h>
  4. #include <limits.h>
  5.  
  6. typedef struct List List;
  7. typedef struct ListNode ListNode;
  8.  
  9. struct ListNode {
  10.     List *list;
  11.     ListNode *next;
  12.     ListNode *prev;
  13. };
  14.  
  15. void ListNode_init (ListNode *node) {
  16.     node->next = 0;
  17.     node->prev = 0;
  18.     node->list = 0;
  19. }
  20.  
  21. void ListNode_separate (ListNode *node) {
  22.     if (node->list == 0) return;
  23.     node->next->prev = node->prev;
  24.     node->prev->next = node->next;
  25.     ListNode_init(node);
  26. }
  27.  
  28. struct List {
  29.     ListNode head;
  30. };
  31.  
  32. void List_init (List *l) {
  33.     l->head.list = l;
  34.     l->head.next = &l->head;;
  35.     l->head.prev = &l->head;;
  36. }
  37.  
  38. int List_member (List *l, ListNode *node) {
  39.     return node->list == l;
  40. }
  41.  
  42. int List_empty (List *l) {
  43.     return l->head.next == &l->head;
  44. }
  45.  
  46. ListNode * List_front (List *l) {
  47.     return l->head.next;
  48. }
  49.  
  50. ListNode * List_end (List *l) {
  51.     return &l->head;
  52. }
  53.  
  54. void List_add (List *l, ListNode *node) {
  55.     if (node->list) ListNode_separate(node);
  56.     node->next = l->head.prev->next;
  57.     l->head.prev->next = node;
  58.     node->prev = l->head.prev;
  59.     l->head.prev = node;
  60.     node->list = l;
  61. }
  62.  
  63. #define ALPHABET_SIZE UCHAR_MAX
  64. ListNode letters[ALPHABET_SIZE];
  65. List list1;
  66. List list2;
  67.  
  68. const char *printable (int x) {
  69.     static char buf[5] = " ' '";
  70.     if (!isprint(x)) return " .";
  71.     buf[2] = x;
  72.     return buf;
  73. }
  74.  
  75. void dump_list (List *l) {
  76.     if (l == &list1) printf("list1: ");
  77.     else printf("list2: ");
  78.     ListNode *node = List_front(l);
  79.     while (node != List_end(l)) {
  80.         printf("%s", printable(node - letters));
  81.         node = node->next;
  82.     }
  83.     puts("");
  84. }
  85.  
  86. int main (int argc, char *argv[]) {
  87.     const char *input = "the quick brown fox jumped over the lazy dog";
  88.     const unsigned char *p;
  89.     if (argc > 1) input = argv[1];
  90.     List_init(&list1);
  91.     List_init(&list2);
  92.     for (p = (const void *)input; *p; ++p) {
  93.         int c = tolower(*p);
  94.         if (!isalpha(c)) continue;
  95.         ListNode *node = &letters[c];
  96.         if (List_member(&list1, node)) {
  97.             List_add(&list2, node);
  98.         } else if (!List_member(&list2, node)) {
  99.             List_add(&list1, node);
  100.         }
  101.     }
  102.     if (List_empty(&list1)) {
  103.         puts("No non-repeating letters.");
  104.     } else {
  105.         char x = List_front(&list1) - letters;
  106.         printf("first non-repeating char: %#04x%s\n", x, printable(x));
  107.     }
  108.     return 0;
  109. }
Success #stdin #stdout 0s 2248KB
comments ()
stdin 
Standard input is empty
stdout 
first non-repeating char: 0x71 'q'
https://ideone.com/cLN0XI
language:
C99 (gcc 8.3)
created:
11 years ago
visibility:
public

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