day5

day5/input.txt.h

@@ -0,0 +1,15 @@
+#pragma once
+
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+extern uint32_t _binary_day5_input_txt_start __asm("_binary_day5_input_txt_start");
+extern uint32_t _binary_day5_input_txt_end __asm("_binary_day5_input_txt_end");
+extern uint32_t _binary_day5_input_txt_size __asm("_binary_day5_input_txt_size");
+
+#ifdef __cplusplus
+}
+#endif

day5/sample1.txt

@@ -0,0 +1,28 @@
+47|53
+97|13
+97|61
+97|47
+75|29
+61|13
+75|53
+29|13
+97|29
+53|29
+61|53
+97|53
+61|29
+47|13
+75|47
+97|75
+47|61
+75|61
+47|29
+75|13
+53|13
+
+75,47,61,53,29
+97,61,53,29,13
+75,29,13
+75,97,47,61,53
+61,13,29
+97,13,75,29,47

day5/sample1.txt.h

@@ -0,0 +1,15 @@
+#pragma once
+
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+extern uint32_t _binary_day5_sample1_txt_start __asm("_binary_day5_sample1_txt_start");
+extern uint32_t _binary_day5_sample1_txt_end __asm("_binary_day5_sample1_txt_end");
+extern uint32_t _binary_day5_sample1_txt_size __asm("_binary_day5_sample1_txt_size");
+
+#ifdef __cplusplus
+}
+#endif

day5/solution.c

@@ -0,0 +1,126 @@
+#include <stdbool.h>
+
+#include "parse.h"
+#include "printf.h"
+
+struct rule {
+  char l;
+  char r;
+};
+
+static void error(void)
+{
+  printf("day5: invalid input\n");
+  while (1);
+}
+
+static const char * parse_rules(const char * input, const char * end,
+                                struct rule * rules, int * rules_length)
+{
+  int i = 0;
+
+  while (input < end) {
+    int num;
+    input = parse_base10(input, &num);
+    if (*input++ != '|') { error(); }
+    rules[i].l = num;
+
+    input = parse_base10(input, &num);
+    if (*input++ != '\n') { error(); }
+    rules[i].r = num;
+
+    i += 1;
+
+    if (*input == '\n')
+      break; // end of rules
+  }
+
+  *rules_length = i;
+
+  return parse_skip(input, '\n');
+}
+
+static const char * parse_update(const char * input, const char * end,
+                                 char * update, int * update_length)
+{
+  int i = 0;
+  while (input < end) {
+    int num;
+    input = parse_base10(input, &num);
+    input = parse_skip(input, ',');
+
+    update[i] = num;
+    i += 1;
+
+    if (*input == '\n')
+      break; // end of update
+  }
+
+  *update_length = i;
+
+  return parse_skip(input, '\n');
+}
+
+static bool rule_match(const struct rule * rule, int a, int b)
+{
+  return rule->l == a && rule->r == b;
+}
+
+static bool sort_numbers(const struct rule * rules, int rules_length,
+                         char * nums, int nums_length)
+{
+  bool at_least_one_swap = false;
+  while (true) {
+    bool swapped = false;
+    for (int i = 0; i < nums_length - 1; i++) {
+      int a = nums[i + 0];
+      int b = nums[i + 1];
+
+      for (int j = 0; j < rules_length; j++) {
+        if (rule_match(&rules[j], b, a)) {
+          swapped = true;
+          at_least_one_swap = true;
+          nums[i + 0] = b;
+          nums[i + 1] = a;
+        }
+      }
+    }
+    if (!swapped)
+      break;
+  }
+
+  return at_least_one_swap;
+}
+
+static int solve(const char * input, int length, bool correctly_ordered)
+{
+  const char * end = input + length;
+
+  struct rule rules[1200];
+  int rules_length;
+  input = parse_rules(input, end, rules, &rules_length);
+
+  int sum = 0;
+  char update[24];
+  while (input < end) {
+    int update_length;
+    input = parse_update(input, end, update, &update_length);
+
+    bool at_least_one_swap = sort_numbers(rules, rules_length, update, update_length);
+    if (correctly_ordered ^ at_least_one_swap) {
+      sum += update[update_length / 2];
+    }
+  }
+
+  return sum;
+}
+
+int day5_part1(const char * input, int length)
+{
+  return solve(input, length, true);
+}
+
+int day5_part2(const char * input, int length)
+{
+  return solve(input, length, false);
+}

input_dreamcast.inc

@@ -7,6 +7,8 @@
 #include "day3/input.txt.h"
 #include "day4/sample1.txt.h"
 #include "day4/input.txt.h"
+#include "day5/sample1.txt.h"
+#include "day5/input.txt.h"
 
 static struct start_size sample[][2] = {
   {
@@ -33,6 +35,12 @@ static struct start_size sample[][2] = {
     { (  char *)&_binary_day4_sample1_txt_start,
       (uint32_t)&_binary_day4_sample1_txt_size   },
   },
+  {
+    { (  char *)&_binary_day5_sample1_txt_start,
+      (uint32_t)&_binary_day5_sample1_txt_size   },
+    { (  char *)&_binary_day5_sample1_txt_start,
+      (uint32_t)&_binary_day5_sample1_txt_size   },
+  },
 };
 
 static struct start_size input[] = {
@@ -44,4 +52,6 @@ static struct start_size input[] = {
     (uint32_t)&_binary_day3_input_txt_size   },
   { (  char *)&_binary_day4_input_txt_start,
     (uint32_t)&_binary_day4_input_txt_size   },
+  { (  char *)&_binary_day5_input_txt_start,
+    (uint32_t)&_binary_day5_input_txt_size   },
 };

runner.inc

@@ -6,10 +6,13 @@ int day3_part1(char * input, int length);
 int day3_part2(char * input, int length);
 int day4_part1(char * input, int length);
 int day4_part2(char * input, int length);
+int day5_part1(char * input, int length);
+int day5_part2(char * input, int length);
 
 part_func solution[][2] = {
   {day1_part1, day1_part2},
   {day2_part1, day2_part2},
   {day3_part1, day3_part2},
   {day4_part1, day4_part2},
+  {day5_part1, day5_part2},
 };

runner_dreamcast.cpp

@@ -370,7 +370,7 @@ int main()
       done = true;
       done_frame = frame;
     }
-    if (done && (frame == done_frame + 2))
+    if (done && (frame == done_frame + 3))
       break;
   }
 

solutions.mk

@@ -11,4 +11,7 @@ DAY_OBJ = \
 	day3/solution.o \
 	day4/sample1.txt.o \
 	day4/input.txt.o \
-	day4/solution.o
+	day4/solution.o \
+	day5/sample1.txt.o \
+	day5/input.txt.o \
+	day5/solution.o