linked_list.c

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

struct list_node_s {
   int    data;
   struct list_node_s* next;
};

int  Insert(int value, struct list_node_s** head_p);
void Print(struct list_node_s* head_p);
int  Member(int value, struct list_node_s* head_p);
int  Delete(int value, struct list_node_s** head_p);
void Free_list(struct list_node_s** head_p);
int  Is_empty(struct list_node_s* head_p);
char Get_command(void);
int  Get_value(void);


int main(void) {
   char command;
   int  value;
   struct list_node_s* head_p = NULL;  
   command = Get_command();
   while (command != 'q' && command != 'Q') {
      switch (command) {
         case 'i': 
         case 'I': 
            value = Get_value();
            Insert(value, &head_p); 
            break;
         case 'p':
         case 'P':
            Print(head_p);
            break;
         case 'm': 
         case 'M':
            value = Get_value();
            Member(value, head_p);  
            break;
         case 'd':
         case 'D':
            value = Get_value();
            Delete(value, &head_p); 
            break;
         default:
            printf("There is no %c command\n", command);
            printf("Please try again\n");
      }
      command = Get_command();
   }
   Free_list(&head_p);

   return 0;
}              
int Insert(int value, struct list_node_s** head_pp) {
   struct list_node_s* curr_p = *head_pp;
   struct list_node_s* pred_p = NULL;
   struct list_node_s* temp_p;
   
   while (curr_p != NULL && curr_p->data < value) {
      pred_p = curr_p;
      curr_p = curr_p->next;
   }

   if (curr_p == NULL || curr_p->data > value) {
      temp_p = malloc(sizeof(struct list_node_s));
      temp_p->data = value;
      temp_p->next = curr_p;
      if (pred_p == NULL)
         *head_pp = temp_p;
      else
         pred_p->next = temp_p;
      return 1;
   } else { /* value in list */
      printf("%d is already in the list\n", value);
      return 0;
   }
}  
void Print(struct list_node_s* head_p) {
   struct list_node_s* curr_p;

   printf("list = ");

   curr_p = head_p;
   while (curr_p != (struct list_node_s*) NULL) {
      printf("%d ", curr_p->data);
      curr_p = curr_p->next;
   }
   printf("\n");
} 
int  Member(int value, struct list_node_s* head_p) {
   struct list_node_s* curr_p;

   curr_p = head_p;
   while (curr_p != NULL && curr_p->data < value)
      curr_p = curr_p->next;

   if (curr_p == NULL || curr_p->data > value) {
      printf("%d is not in the list\n", value);
      return 0;
   } else {
      printf("%d is in the list\n", value);
      return 1;
   }
} 
int Delete(int value, struct list_node_s** head_pp) {
   struct list_node_s* curr_p = *head_pp;
   struct list_node_s* pred_p = NULL;

	//Encuentra el valor
   while (curr_p != NULL && curr_p->data < value) {
      pred_p = curr_p;
      curr_p = curr_p->next;
   }
   
   if (curr_p != NULL && curr_p->data == value) {
      if (pred_p == NULL) { //primer elemento en la lista
         *head_pp = curr_p->next;
#        ifdef DEBUG
         printf("Freeing %d\n", value);
#        endif
         free(curr_p);
      } else { 
         pred_p->next = curr_p->next;
#        ifdef DEBUG
         printf("Freeing %d\n", value);
#        endif
         free(curr_p);
      }
      return 1;
   } else {
   printf("%d is not in the list\n", value);
      return 0;
   }
}  
void Free_list(struct list_node_s** head_pp) {
   struct list_node_s* curr_p;
   struct list_node_s* succ_p;

   if (Is_empty(*head_pp)) return;
   curr_p = *head_pp; 
   succ_p = curr_p->next;
   while (succ_p != NULL) {
#     ifdef DEBUG
      printf("Freeing %d\n", curr_p->data);
#     endif
      free(curr_p);
      curr_p = succ_p;
      succ_p = curr_p->next;
   }
#  ifdef DEBUG
   printf("Freeing %d\n", curr_p->data);
#  endif
   free(curr_p);
   *head_pp = NULL;
}  

int  Is_empty(struct list_node_s* head_p) {
   if (head_p == NULL)
      return 1;
   else
      return 0;
}  

char Get_command(void) {
   char c;

   printf("Please enter a command:  ");
   scanf(" %c", &c);
   return c;
} 

int  Get_value(void) {
   int val;

   printf("Please enter a value:  ");
   scanf("%d", &val);
   return val;
}