usaa24/cv4/a_train.c

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

struct car* add_car(struct car* first,const char* target)
{
    struct car* newcar = calloc(1,sizeof(struct car));
    strcpy(newcar->value, target);

    if(first == NULL)
    {
        return newcar;
    }

    struct car* this = first;
    
    while(this->next != NULL)
    {
        this = this->next;
    }

    this->next = newcar;

    return first;
}

void print_train(struct car* first)
{
    if(first == NULL)
    {
        return;
    }
    struct car* this = first;
    
    while(this->next != NULL)
    {
        printf("%s\n", this->value);
        this = this->next;
    }
    printf("%s\n", this->value);
}

void cancel_train(struct car* first)
{
    if(first == NULL)
    {
        return;
    }
    struct car* this = first;
    if(this->next != NULL)
    {
        cancel_train(this->next);
    }
    free(first);
}


struct car* clear_train(struct car* first, const char* target)
{
    if(first == NULL)
    {
        return NULL;
    }
    if(first->next == NULL)
    {
        if(!strcmp(target, first->value))
        {
            free(first);
            //first = NULL;
            return NULL;
        }
        else
        {
            return first;
        }
    }
    struct car* prev = first;

    if(prev->next->next == NULL)
    {
        if(!strcmp(prev->value, target))
        {
            struct car* second = prev->next;
            free(prev);
            first = second;
            return first;
        }
        else if(!strcmp(prev->next->value, target))
        {
            free(prev->next);
            return first;
        }
        else
        {
            return first;
        }
    }

    while (prev->next->next != NULL)
    {
        if(strcmp(prev->value, target))
        {
            struct car* third = prev->next->next;
            free(prev->next);
            prev->next = third;
            return first;
        }
        prev = prev->next;
    }
	return first;
}