fruitsort.c

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

struct node;
struct edge;

struct node {
	char *name;
	struct edge *edges;
};

struct edge {
	struct node *node;
	struct edge *next;
};

static struct edge * create_edge (struct node *to) {
	struct edge *edge = malloc (sizeof *edge);
	if (edge) {
		edge->node = to;
		edge->next = NULL;
	}
	return edge;
}

static void add_edge (struct edge **to, struct edge *edge) {
	if (to && edge) {
		edge->next = *to;
		*to = edge;
	}
}


int main (void) {
	static char *elements[] = { "alpha", "bravo", "charlie", "delta" };

	int size = sizeof elements / sizeof *elements;
	struct node *nodes[size];

	for (int i = 0; i < size; i++) {
		nodes[i] = malloc (sizeof *nodes);
		if (!nodes[i]) return EXIT_FAILURE;
		nodes[i]->name = elements[i];
		nodes[i]->edges = NULL;
	}

	for (int a = 0; a < size; a++) {
		for (int b = a + 1; b < size; b++) {
			char code;
			int better, worse;

			printf ("Which is better? [A]: %s  [B]: %s  $ ", nodes[a]->name, nodes[b]->name);
			while (isspace (code = getchar ()));

			code = tolower (code);
			if (code == 'a') {
				better = a;
				worse = b;
			} else if (code == 'b') {
				better = b;
				worse = a;
			} else {
				return EXIT_FAILURE;
			}

			add_edge (&nodes[better]->edges, create_edge (nodes[worse]));
		}
	}

	for (int i = 0; i < size; i++) {
		struct edge *edge;
		printf ("\n%s is better than:\n", nodes[i]->name);

		edge = nodes[i]->edges;
		if (edge) {
			while (edge) {
				printf ("\t - %s\n", edge->node->name);
				edge = edge->next;
			}
		} else {
			puts ("\tjack-squat");
		}
	}

	return 0;
}