usaa20/cv6/a_train.c

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

int getLength(struct car* first) {

	if (first != NULL) {

		int count = 1;

		while (first->next != NULL) {

			count++;
			first = first->next;

		}

		return count;

	} else {

		return 0;

	}

}

struct car* getLast(struct car* first) {

	if (first == NULL) return NULL;

	while (first->next != NULL) first = first->next;

	return first;

}

struct car* getLastButOne(struct car* first) {

	if (first == NULL || first->next == NULL) return NULL;

	while (first->next->next != NULL) first = first->next;

	return first;

}

struct car* add_car(struct car* first, const char* target) {

	struct car* newcar = calloc(1,sizeof(struct car));

	strcpy(newcar->value, target);
	newcar->next = NULL;

	if (first == NULL) return newcar;

	struct car* last = getLast(first);

	last->next = newcar;

	return first;

}

void print_train(struct car* first) {

	if (first == NULL) return;

	struct car* this = first;

	printf("\nTrain way:\n\n");
	printf("%s", this->value);

	while (this->next != NULL) {

		this = this->next;
		printf(" -> ");
		printf("%s", this->value);

	}

	printf("\n\n");

}

void popBack(struct car* first) {

	if (first == NULL) { printf("123"); return; }

	struct car* lastbo = getLastButOne(first);

	if (lastbo == NULL) {
		
		free(first);
		first = NULL;

	} else {

		free(lastbo->next);
		lastbo->next = NULL;

	}

}

void cancel_train(struct car* first) {

	if (first == NULL) return;

	while (first->next != NULL) popBack(first);

	free(first);
	first = NULL;

}

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

	if (first == NULL) return NULL;

	// while (first->next->next != NULL) {

	// 	if (strcmp(first->next->value, target) == 0) {

	// 		struct car* node = first->next->next;

	// 		free(first->next);

	// 		first->next = node;

	// 	}

	// }

	struct car* this = first;

	if (strcmp(first->value, target) == 0) {

		this = this->next;

		free(first);

	}

	return this;

}