usaa21/cv4/a_train.c

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

struct car* add_car(struct car* first,const char* target) {
    struct car* new_car = (struct car*)calloc(1,sizeof(struct car));
    strcpy(new_car->value, target);
    new_car->next = NULL;
    if (first == NULL){
        first = new_car;
    }
    else {
	struct car* temp=first;
	while(temp->next != NULL){
	    temp = temp->next;
	}
	temp->next = new_car;
    }
    return first;
}

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

}

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

}


struct car* clear_train(struct car* first, const char* target) {
	struct car* this = first;
	if (this == NULL){
		return NULL;
	}
	if (this->next == NULL){
		if(strcmp(this->value, target) == 0){
			free(this);
			return NULL;
		}else {
			return this;
		}
	}
	while( this->next->next != NULL){
		if(strcmp(this->next->value, target) == 0){
			struct car* third = this->next->next;
			free(this->next);
			this->next = third; 
			return this;
		}
		else {
			this = this->next;
		}
	}
	if(strcmp(this->value, target) == 0){
		struct car* tmp = this->next;
		free(this);
		return tmp;
	}else if(strcmp(this->next->value, target) == 0){
		free(this->next);
		this->next=NULL;
		return first;
	} 
	return first;
}