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Day 12 solutions
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12/12-1and2.c
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250
12/12-1and2.c
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#include <stdlib.h>
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#include <stdio.h>
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#include <stdbool.h>
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#include <string.h>
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#include <ctype.h>
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#define PART_2
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#define ADJACENT_NODE_SIZE 8 // MAX NUMBER OF CONNECTED NODES
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#define MAX_CAVES 20
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#define NAME_BUF 5
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#ifdef PART_2
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#define MAX_VISITS 2
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#else
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#define MAX_VISITS 1
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#endif
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// ASSUME STRING IS EITHER ALL UPPERCASE OR ALL LOWERCASE
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size_t max_visits(char *name)
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{
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if (strcmp(name, "start") == 0 || strcmp(name, "end") == 0)
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return 1;
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else if (isupper(name[0]) != 0)
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return 0;
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return MAX_VISITS; // LOWERCASE
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}
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typedef struct __node
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{
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char *name;
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size_t max_visits; // 0 => INFINITE VISITS
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size_t visit_count;
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struct __node **linked;
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size_t id;
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int n_linked;
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} NODE;
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NODE *new_node(char *name, size_t id)
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{
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NODE *p_node = calloc(1, sizeof(NODE));
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p_node->name = name;
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p_node->max_visits = max_visits(name);
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p_node->visit_count = 0;
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p_node->id = id;
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p_node->linked = calloc(ADJACENT_NODE_SIZE, sizeof(NODE *));
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p_node->n_linked = 0;
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return p_node;
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}
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void link_nodes(NODE *node1, NODE *node2)
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{
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node2->linked[node2->n_linked] = node1;
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node1->linked[node1->n_linked] = node2;
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node1->n_linked++;
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node2->n_linked++;
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}
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// NOTE - A HASHTABLE WOULD WORK GREAT FOR VERY LARGE SYSTEMS, BUT SINCE
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// THE CHALLENGE IS SMALL WE WILL USE A SIMPLE LIST.
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typedef struct
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{
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NODE **nodes;
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int n_nodes;
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NODE *start_node;
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NODE *end_node;
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} CAVE_SYSTEM;
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CAVE_SYSTEM *new_cave_system()
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{
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CAVE_SYSTEM *p_cave_system = calloc(1, sizeof(CAVE_SYSTEM));
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p_cave_system->nodes = calloc(MAX_CAVES, sizeof(NODE *));
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}
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int add_new_cave(CAVE_SYSTEM *caves, char *name)
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{
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if (caves->n_nodes > MAX_CAVES)
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exit(EXIT_FAILURE);
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for (int i = 0; i < caves->n_nodes; i++)
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if (strcmp(name, caves->nodes[i]->name) == 0)
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return i;
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caves->nodes[caves->n_nodes] = new_node(name, caves->n_nodes);
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if (caves->start_node == NULL && strcmp(name, "start") == 0)
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caves->start_node = caves->nodes[caves->n_nodes];
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else if (caves->end_node == NULL && strcmp(name, "end") == 0)
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caves->end_node = caves->nodes[caves->n_nodes];
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caves->n_nodes++;
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return caves->n_nodes - 1;
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}
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void print_links(CAVE_SYSTEM *caves)
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{
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for (size_t i = 0; i < caves->n_nodes; i++)
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{
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printf("%s:\t", caves->nodes[i]->name);
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for (size_t j = 0; caves->nodes[i]->linked[j] != NULL; j++)
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{
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printf("%s ", caves->nodes[i]->linked[j]->name);
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}
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putchar('\n');
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}
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}
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// READ INPUT CAVES
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void read_link(CAVE_SYSTEM *system, char *link_description)
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{
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char buf1[NAME_BUF];
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int cave1_idx, cave2_idx;
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char buf2[NAME_BUF];
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sscanf(link_description, "%[^-]-%[^\n]\n", buf1, buf2);
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cave1_idx = add_new_cave(system, strdup(buf1));
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cave2_idx = add_new_cave(system, strdup(buf2));
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link_nodes(system->nodes[cave1_idx], system->nodes[cave2_idx]);
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}
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CAVE_SYSTEM *read_file(char *input)
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{
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CAVE_SYSTEM *p_caves = new_cave_system();
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FILE *p_file = fopen(input, "r");
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char buf[BUFSIZ];
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while (fgets(buf, sizeof buf, p_file) != NULL)
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read_link(p_caves, buf);
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return p_caves;
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}
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//
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// CAVE TRAVERSAL LOGIC
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//
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typedef struct
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{
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NODE **excluded_nodes;
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NODE **path;
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int path_len;
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int n_paths;
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#ifdef PART_2
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int n_double_visits;
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#endif
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} TRAVERSAL_CONTEXT;
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TRAVERSAL_CONTEXT *new_traversal_context(void)
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{
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TRAVERSAL_CONTEXT *p_context = calloc(1, sizeof(TRAVERSAL_CONTEXT));
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p_context->excluded_nodes = calloc(MAX_CAVES, sizeof(NODE *));
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p_context->path = calloc(MAX_VISITS * MAX_CAVES, sizeof(NODE *));
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p_context->path_len = 0;
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p_context->n_paths = 0;
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#ifdef PART_2
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p_context->n_double_visits = 0;
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#endif
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return p_context;
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}
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void print_path_stack(TRAVERSAL_CONTEXT *context)
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{
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for (size_t i = 0; i < context->path_len; i++)
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printf("%s -> ", context->path[i]->name);
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putchar('\n');
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}
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bool excluded(TRAVERSAL_CONTEXT *context, NODE *node)
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{
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for (size_t i = 0; i < MAX_CAVES; i++)
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{
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if (context->excluded_nodes != NULL && context->excluded_nodes[i] == node)
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return true;
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}
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return false;
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}
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void remove_excluded(TRAVERSAL_CONTEXT *context, NODE *node)
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{
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for (size_t i = 0; i < MAX_CAVES; i++)
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if (context->excluded_nodes != NULL && context->excluded_nodes[i] == node)
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{
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context->excluded_nodes[i] = NULL;
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#ifdef PART_2
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context->n_double_visits--;
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#endif
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}
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}
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void add_excluded(TRAVERSAL_CONTEXT *context, NODE *node)
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{
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for (size_t i = 0; i < MAX_CAVES; i++)
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if (context->excluded_nodes[i] != NULL)
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{
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if (context->excluded_nodes[i] == node)
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return;
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}
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else
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{
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context->excluded_nodes[i] = node;
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#ifdef PART_2
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if (node->max_visits == MAX_VISITS)
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context->n_double_visits++;
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#endif
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return;
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}
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}
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void finish_node(NODE *node, TRAVERSAL_CONTEXT *context)
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{
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if (node->max_visits > 0)
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{
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node->visit_count--;
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if (node->visit_count < node->max_visits)
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remove_excluded(context, node);
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}
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context->path_len--;
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}
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void traverse(NODE *start, TRAVERSAL_CONTEXT *context)
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{
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context->path[context->path_len] = start;
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context->path_len++;
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start->visit_count++;
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#ifdef PART_2
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if (context->n_double_visits > 1 || excluded(context, start))
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#else
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if (excluded(context, start))
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#endif
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{
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finish_node(start, context);
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return;
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}
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if (strcmp(start->name, "end") == 0)
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{
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// printf("%s : ", start->name);
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// print_path_stack(context);
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context->n_paths++;
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finish_node(start, context);
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return;
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}
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if (start->max_visits > 0 && start->visit_count >= start->max_visits)
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add_excluded(context, start);
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for (size_t i = 0; start->linked[i] != NULL; i++)
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traverse(start->linked[i], context);
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finish_node(start, context);
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}
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int main(int argc, char const *argv[])
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{
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CAVE_SYSTEM *p_caves = read_file("input");
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print_links(p_caves);
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TRAVERSAL_CONTEXT *p_context = new_traversal_context();
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traverse(p_caves->start_node, p_context);
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printf("n_paths : %d\n", p_context->n_paths);
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return 0;
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}
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