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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <string.h>
  4.  
  5. #define HASHSIZE 101
  6.  
  7. static struct Nlist *hashtab[HASHSIZE]; // pointer table
  8.  
  9. struct Nlist {
  10. 	struct Nlist *next; // next entry in chain
  11. 	char *name; // defined name
  12. 	char *defn; // replacement text
  13. };	
  14.  
  15. char *strdup(char *s)
  16. {
  17. 	char *tmp = malloc(strlen(s) + 1);
  18. 	if(tmp != NULL) 
  19. 		strcpy(tmp, s);
  20. 	return tmp;
  21. }
  22.  
  23. unsigned hash(char *s) 
  24. {
  25. 	unsigned hashval;
  26.  
  27. 	for(hashval = 0; *s != '\0'; s++) 
  28. 		hashval = *s + 31 * hashval;
  29. 	return hashval % HASHSIZE;
  30. }
  31.  
  32. struct Nlist *lookup(char *s, struct Nlist **previous)
  33. {
  34. 	struct Nlist *np;
  35. 	int i = 0;
  36. 	*previous = NULL;
  37.  
  38. 	for(np = hashtab[hash(s)]; np != NULL; np = np->next, i++)
  39. 		if(strcmp(s, np->name) == 0)
  40. 			return np;
  41. 		if(i > 0) 
  42. 			*previous = np;
  43.  
  44. 	return NULL;
  45. }
  46.  
  47. struct Nlist *install(char *name, char *defn)
  48. {
  49. 	struct Nlist *np;
  50. 	struct Nlist *tmp;
  51. 	unsigned hashval;
  52.  
  53. 	if((np = lookup(name, &tmp)) == NULL) {
  54. 		np = malloc(sizeof(*np));
  55. 		if(np == NULL || (np->name = strdup(name)) == NULL)
  56. 			return NULL;
  57. 		hashval = hash(name);
  58. 		np->next = hashtab[hashval];
  59. 		hashtab[hashval] = np;
  60. 	} else {
  61. 		free(np->defn);
  62. 	}
  63.  
  64. 	if((np->defn = strdup(defn)) == NULL)
  65. 		return NULL;
  66. 	return np;
  67. }
  68.  
  69. void printList(char *name)
  70. {
  71. 	for(struct Nlist *tmp = hashtab[hash(name)]; tmp != NULL; tmp = tmp->next) { 
  72. 		printf("%s\n", tmp->name);
  73. 	}
  74. }
  75.  
  76. void undef(char *name)
  77. {
  78. 	struct Nlist *tmp  = hashtab[hash(name)];
  79.  
  80. 	if(!strcmp(tmp->name, name)) { // delete the head node
  81. 		hashtab[hash(name)] = tmp->next;
  82. 		free(tmp->name);
  83. 		free(tmp);
  84.  
  85. 		return;
  86. 	}
  87.  
  88. 	for(; strcmp(tmp->next->name, name); tmp = tmp->next)
  89. 		;
  90.  
  91. 	struct Nlist *save = tmp->next; // save the desired node for deletion
  92. 	tmp->next          = tmp->next->next; // adjust the links
  93. 	free(save->name);
  94. 	free(save);
  95. }
  96.  
  97.  
  98. int main() 
  99. {
  100. 	install("test", "11");
  101. 	install("estt", "qwe");
  102. 	install("tset", "2323");
  103. 	//undef("test");
  104.  
  105. 	undef("test");
  106. 	printList("test");
  107.  
  108. 	return 0;
  109. }
  110.  
  111.  
Success #stdin #stdout 0s 2420KB
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https://ideone.com/t0bjiA
language:
C99 (gcc 8.3)
created:
10 years ago
visibility:
public

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