usaa24/cv4/a_train.c

#include <stdio.h>
#include"a_train.h"



struct car* add_car(struct car* first,const char* target)
{
    struct car* ret=first;
    struct car* nc=(struct car*) malloc(sizeof(struct car)); 
    strcpy(nc->value, target);
    nc->next=NULL;

    if(first)
    {
        while(first->next!=NULL)
        {    
            first=first->next;
        }
        first->next=nc;
        return ret;
    }
    
    first=nc;  

    return first;
}

void print_train(struct car* first)
{
    if(first==NULL)
    {
        
        return;
    }

    do
    {
        printf("%s", first->value);
        first=first->next;
        if(first) printf("->");
    }while(first!=NULL);

}

void cancel_train(struct car* first)
{
    struct car* t;
    while(first!=NULL)
    {
        t=first;
        first=first->next;
        free(t);
    }
}

struct car* clear_train(struct car* first, const char* target)
{
    struct car* t;  
    struct car* ptr;  

    if(first==NULL || target==NULL)
    {
        return first;
    }
   
    while(strcmp(first->value, target)==0) 
    {
        t=first;
        first=first->next;
        free(t);
        
        if(first==NULL)
        {
            
           return NULL;
        }        
    }

      
    ptr=first;
   
    do
    {
        if(strcmp(ptr->next->value, target)==0)
        {
            t=ptr->next;;
            ptr->next = ptr -> next->next;
            free(t);
        }
        else
        {
            ptr = ptr -> next;
        }
    }while(ptr->next);


	return first;
}