106 lines
2.2 KiB
C
106 lines
2.2 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <stdbool.h>
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#include "../../lib/aoc.h"
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typedef struct Rule {
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int first;
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int last;
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} Rule;
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typedef struct Rules {
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Rule rule[1200];
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int length;
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} Rules;
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typedef struct Update {
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int page[100];
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int length;
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} Update;
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bool valid_rule(Rule *rule, Update *update) {
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int first = -1, last = -1;
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for (int i = 0; i < update->length; i++) {
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if (rule->first == update->page[i]) first = i;
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if (rule->last == update->page[i]) last = i;
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if (first != -1 && last != -1) return first < last;
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}
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return true;
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}
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bool valid_update(Rules *rules, Update *update) {
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for (int i = 0; i < rules->length; i++) {
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if (!valid_rule(&(rules->rule[i]), update)) return false;
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}
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return true;
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}
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int middle_page_number(Update *update) {
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return update->page[update->length / 2];
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}
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void reorder_update(Rules *rules, Update *update) {
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bool dirty = true;
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while (dirty) {
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dirty = false;
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for (int i = 0; i < update->length - 1; i++) {
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for (int j = 0; j < rules->length; j++) {
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Rule rule = rules->rule[j];
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if (update->page[i] == rule.last && update->page[i + 1] == rule.first) {
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dirty = true;
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update->page[i] = rule.first;
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update->page[i + 1] = rule.last;
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break;
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}
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}
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}
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}
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}
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int main() {
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char *line;
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int sum = 0;
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int reorder_sum = 0;
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Rules rules;
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int first, last;
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Update update;
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char *update_element;
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bool scanning_rules = true;
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while ((line = aoc_read_line()) != NULL) {
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if (scanning_rules) {
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if (strlen(line) == 0) scanning_rules = false;
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else {
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sscanf(line, "%d|%d", &first, &last);
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rules.rule[rules.length].first = first;
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rules.rule[rules.length].last = last;
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rules.length++;
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}
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} else {
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update.length = 0;
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update_element = strtok(line, ",");
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while(update_element != NULL) {
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update.page[update.length++] = atoi(update_element);
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update_element = strtok(NULL, ",");
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}
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if (valid_update(&rules, &update)) sum += middle_page_number(&update);
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else {
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reorder_update(&rules, &update);
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reorder_sum += middle_page_number(&update);
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}
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}
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}
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printf("Part 1: %d\n", sum);
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printf("Part 2: %d\n", reorder_sum);
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aoc_free();
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return 0;
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}
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