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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <string.h>
  4.  
  5. struct node {
  6.   char *data;
  7.   struct node *next;
  8.   struct node *prev;
  9. };
  10.  
  11. void push_head(struct node **root, char *data) {
  12.   struct node *p;
  13.   if ((p = malloc(sizeof(struct node))) != 0) {
  14.     p->data = data;
  15.     if (*root == 0) {
  16.       p->next = p;
  17.       p->prev = p;
  18.     } else {
  19.       p->next = *root;
  20.       p->prev = (*root)->prev;
  21.       p->prev->next = p;
  22.       p->next->prev = p;
  23.     }
  24.     *root = p;
  25.   }
  26. }
  27.  
  28. void push_tail(struct node **root, char *data) {
  29.   struct node *p;
  30.   if ((p = malloc(sizeof(struct node))) != 0) {
  31.     p->data = data;
  32.     if (*root == 0) {
  33.       p->next = p;
  34.       p->prev = p;
  35.       *root = p;
  36.     } else {
  37.       p->next = *root;
  38.       p->prev = (*root)->prev;
  39.       p->prev->next = p;
  40.       p->next->prev = p;
  41.     }
  42.   }
  43. }
  44.  
  45. char *pop(struct node **root) {
  46.   char *r;
  47.   struct node *p;
  48.   if (*root == 0)
  49.     return 0;
  50.   p = *root;
  51.   r = p->data;
  52.   if (p->next == p) {
  53.     *root = 0;
  54.     free(p);
  55.   } else {
  56.     p->next->prev = p->prev;
  57.     p->prev->next = p->next;
  58.     *root = p->next;
  59.     free(p);
  60.   }
  61.   return r;
  62. }
  63.  
  64. #define BUFFSIZE 1024
  65. int main(int argc, char *argv[]) {
  66.   struct node *rootS = 0;
  67.   static char buff[BUFFSIZE];
  68.   char *p;
  69.   int flag_reverse;
  70.   int flagsig;
  71.   if (argc != 2) {
  72.   usage:
  73.     fprintf(stderr, "usage: %s -r/f.\n option -r:reverse, -f:forward\n", argv[0]);
  74.     exit(1);
  75.   }
  76.   if (*argv[1] == '-') {
  77.     if (*(argv[1] + 1) == 'f')
  78.       flag_reverse = 0;
  79.     else if (*(argv[1] + 1) == 'r')
  80.       flag_reverse = 1;
  81.     else
  82.       goto usage;
  83.   } else {
  84.     goto usage;
  85.   }
  86.   rootS = 0;
  87.   for (;fgets(buff, BUFFSIZE, stdin);) {
  88.     if ((p = malloc(strlen(buff) + 1)) != 0)
  89.       strcpy(p, buff);
  90.       if (flag_reverse)
  91.         push_head(&rootS, p);
  92.       else
  93.         push_tail(&rootS, p);
  94.   }
  95.   putchar('\n');
  96.   while ((p = pop(&rootS)) != 0) {
  97.     printf("%s", p);
  98.     free(p);
  99.   }
  100.   return 0;
  101. }
  102. /* end */
  103.  
Runtime error #stdin #stdout 0.01s 1672KB
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stdin
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Standard input is empty
stdout
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Standard output is empty
https://ideone.com/Gbj0BF
language:
C (gcc 8.3)
created:
12 years ago
visibility:
public

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