usaa20/cv5/a_train.c

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

#include "a_train.h"

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

    if(target == NULL){
        return 0;
    }
    
    if(first == NULL){
        strcpy(newcar->value, target);
        newcar->next = NULL;
        return newcar;
    }
    strcpy(newcar->value,target);
    newcar->next = NULL;    
    struct car *this = first;
    while(this->next != NULL){
        this = this->next;         
    }
    this->next = newcar;
    return first;  
}

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

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



struct car* clear_train(struct car* first, const char* target) {
    if(first == NULL){
        return 0;
    } 

    if(first->next == NULL){
      int result = strcmp(first->value, target);
        if(result == 0){
           free(first);
           return 0;          
       }
    }
    //struct car* this = first;
    /*if(first->next->next == NULL){
        int x = strcmp(this->next->value, target);
        if(x == 0){
            struct car* secondlast = first;
            while(this->next != NULL){
                secondlast = this;
                this = this->next; 
            }
            if(this == first){
                first = NULL;
            }
            else{
                secondlast->next = NULL;
            }
            free(this);
        }
    }  */

    else{
        struct car* this = first;
        while(this != NULL){
            while(this != NULL){
                int x = strcmp(this->value, target);
                if(x == 0){
                    first = this->next;
                    free(this);
                    this->next = NULL;
                    //free(this->next); 
                      
                    return first;    
                }
                this = this->next;
            }
            /*int x = strcmp(this->value, target);
            if(x == 0){ 
                struct car* curr = first;
                struct car* prev = NULL;
                if(first == this){
                    first = this->next;
                    free(this);
                    return first;
                }
                while(curr != this){
                    prev = curr;
                    curr = curr->next;

                } 
                prev->next = curr->next;
                free(this);
            }
            this = this->next;*/
        }
   }
   return first;
}