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

struct thing {
	char *stuff;
	struct thing *another_thing;
};

/*
 * What does this function do?
 */
void
action1(struct thing **yp, const char *stuff)
{
	struct thing *x;

	x = malloc(sizeof(struct thing));
	if (x == NULL) {
		fprintf(stderr, "Memory allocation near line %d failed!\n",
		    __LINE__);
		exit(1);
	}

	/*
	 * Alternatively, the next line of code can be written:
	 * x->stuff = strdup(stuff);
	 */
	x->stuff = malloc(strlen(stuff) + 1);
	if (x->stuff == NULL) {
		fprintf(stderr, "Memory allocation near line %d failed!\n",
		    __LINE__);
		exit(1);
	}
	strcpy(x->stuff, stuff);
	x->another_thing = *yp;
	*yp = x;
}

/*
 * What does this function do?
 */
void
action2(struct thing **yp)
{
	struct thing *x;

	while ((x = *yp) != NULL) {
		printf("%s ", x->stuff);
		yp = &x->another_thing;
	}
	putchar('\n');
}

/*
 * What does this function do?
 */
bool
action3(struct thing **yp, const char *stuff)
{
	struct thing *x;

	while ((x = *yp) != NULL) {
		if (strcmp(x->stuff, stuff) == 0)
			return (true);
		else
			yp = &x->another_thing;
	}
	return (false);
}

/*
 * What does this function do?
 */
void
action4(struct thing **yp, const char *stuff)
{
	struct thing *x;

	while ((x = *yp) != NULL) {
		if (strcmp(x->stuff, stuff) == 0) {
			*yp = x->another_thing;
			free(x->stuff);
			free(x);
			return;
		} else
			yp = &x->another_thing;
	}
}

/*
 * What does this program output?
 */
int
main(void)
{
	struct thing *y = NULL;

	action2(&y);

	action1(&y, "Cox");
	action1(&y, "Alan");
	action1(&y, "Hello");
	action2(&y);

	printf("Hello %d Huh %d\n", action3(&y, "Hello"), action3(&y, "Huh"));

	action4(&y, "Michael");
	action2(&y);

	action4(&y, "Alan");
	action2(&y);
	action4(&y, "Hello");
	action2(&y);
	action4(&y, "Cox");
	action2(&y);

	action1(&y, "Dave");
	action1(&y, "Johnson");
	action1(&y, "Hello");
	action2(&y);

	return (0);
}