sortlist.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>

struct entry {
  char name[32];
  char sex;
  int  age;
  struct entry *next;
};

struct entry *CreateEntry()
{
  struct entry *ep;

  ep = (struct entry *)malloc(sizeof(struct entry));
  ep->next = NULL;
  return ep;
}

struct entry *ReadEntryData(struct entry *Top)
{
  struct entry *ep;
  char *cp, *tp;
  char buf[512];
  char name[32];
  char sex;
  int age;


  while (fgets(buf, sizeof(buf), stdin) != NULL) {
    /*
     * Node setup
     */
    if (Top == NULL) {
      Top = CreateEntry();
      ep = Top;
    } else {
      for (ep = Top; ep->next != NULL; ep = ep->next);
      ep->next = CreateEntry();
      ep = ep->next;
    }

    cp = buf;
    tp = cp;
    if((cp = index(tp, ' ')) == NULL) {
      fprintf(stderr, "Input format fail: %s\n", tp);
      exit(-1);
    }
    *cp++ = '\0';
    strcpy(ep->name, tp);

    ep->sex = *cp++;
    cp++;

    ep->age = atoi(cp);
  }
  return (Top);
}

int count_list(struct entry *entry_head)
{
  int count;
  struct entry *ep;

  ep = entry_head;
  while (ep != NULL) {
    count++;
    ep = ep->next;
  }

  return (count);
}

struct entry *sortlist(struct entry *entry_head)
{
  struct entry *sorted_head;
  struct entry *sorted_last;
  struct entry *ep_prev;
  struct entry *ep;
  struct entry *min_entry_prev;
  struct entry *min_entry;

  int list_count = count_list(entry_head);
  int i;

  for (i = 0; i < list_count; i++) {
    ep = entry_head;
    min_entry_prev = entry_head;
    min_entry = entry_head;

    while (1) {
      if (ep->age < min_entry->age) {
        min_entry_prev = ep_prev;
        min_entry = ep;
      }
      ep_prev = ep;
      ep = ep->next;

      if (ep == NULL) {
        if (ep_prev == min_entry) {
          min_entry_prev->next = NULL;
        }
        break;
      }
    }

    if (sorted_head == NULL) {
      sorted_head = min_entry;
      sorted_last = min_entry;
    } else {
      sorted_last->next = min_entry;
      sorted_last = min_entry;
    }
    if (min_entry->next != NULL) {
      if (min_entry_prev == min_entry) {
        entry_head = min_entry -> next;
      } else {
        min_entry_prev->next = min_entry->next;
      }
    }
  }

  return (sorted_head);
}

int main()
{
  struct entry *Top;
  struct entry *ep;

  /*
   * read data
   */
  Top = (struct entry *)NULL;
  Top = ReadEntryData(Top);

  /*
   * Print out Entry Data
   */
  printf("Name\tSex\tAge\n");
  for (ep = Top; ep != NULL; ep = ep->next) {
    printf("%s\t%c\t%d\n", ep->name, ep->sex, ep->age);
  }

  /*
   * sorting by age
   */
  Top = sortlist(Top);

  printf("Name\tSex\tAge\n");
  for (ep = Top; ep != NULL; ep = ep->next) {
    printf("%s\t%c\t%d\n", ep->name, ep->sex, ep->age);
  }
}