commit 4406f03bfb6726439fa6aa60c7e93ac62b5b5878
parent e2888de02e7e27fedeb2262cdae8ef67f27c188e
Author: bsandro <brian.drosan@gmail.com>
Date: Sat, 4 Dec 2021 07:16:33 +0200
Day 03, puzzle 2
Diffstat:
3 files changed, 185 insertions(+), 3 deletions(-)
diff --git a/day03/main.c b/day03/main.c
@@ -18,8 +18,8 @@ int main(int argc, char *argv[]) {
int counter1 = puzzle1(filename);
printf("Puzzle #1: %d\n", counter1);
- //int counter2 = puzzle2(filename);
- //printf("Puzzle #2: %d\n", counter2);
+ int counter2 = puzzle2(filename);
+ printf("Puzzle #2: %d\n", counter2);
return 0;
}
diff --git a/day03/puzzle1.c b/day03/puzzle1.c
@@ -13,7 +13,8 @@
#define STR_LEN 13 // BITS_COUNT + 1
#define FMT_STRING "%" FMT(STR_LEN) "s"
-// No idea about the case when number (1/0) counts are equal, it is not described in the task.
+// No idea about the case when number (1/0) counts are equal,
+// it is not described in the task.
int puzzle1(const char *filename) {
FILE *infile = fopen(filename, "r");
diff --git a/day03/puzzle2.c b/day03/puzzle2.c
@@ -0,0 +1,181 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include <strings.h>
+#include <stdbool.h>
+#include <sys/stat.h>
+
+#define PRINT_ERR(func) fprintf(stderr, #func "() error: %s\n", strerror(errno));
+
+#define FMT_(l) #l
+#define FMT(l) FMT_(l)
+
+#define MAX_LEN 16
+#define BITS_COUNT 12
+#define STR_LEN 13 // BITS_COUNT + 1 (EOL/EOF or terminating byte)
+#define FMT_STRING "%" FMT(STR_LEN) "s"
+
+struct numbers_t {
+ long *data;
+ size_t limit;
+ size_t count;
+};
+
+bool init_numbers(struct numbers_t *numbers, size_t limit);
+bool copy_numbers(const struct numbers_t *src, struct numbers_t *dst);
+void move_numbers(struct numbers_t *src, struct numbers_t *dst);
+bool filter_numbers_by_bit(struct numbers_t *numbers, int bit_num, bool (cmp)(size_t, size_t));
+
+bool compare_oxygen(size_t zeroes, size_t ones) {
+ return zeroes > ones;
+}
+
+bool compare_scrubber(size_t zeroes, size_t ones) {
+ return zeroes <= ones;
+}
+
+int puzzle2(const char *filename) {
+ FILE *infile = fopen(filename, "r");
+ if (infile == NULL) {
+ PRINT_ERR(fopen)
+ return -1;
+ }
+
+ struct numbers_t numbers;
+ init_numbers(&numbers, 0);
+
+ // deducing the approx numbers array size from the filesize
+ struct stat filestats = {0};
+ if (stat(filename, &filestats) == -1) {
+ PRINT_ERR(stat)
+ return -1;
+ } else {
+ numbers.limit = filestats.st_size / STR_LEN;
+ numbers.data = calloc(numbers.limit, sizeof(long));
+ if (numbers.data == NULL) {
+ PRINT_ERR(calloc)
+ return -1;
+ }
+ }
+
+ char buf[MAX_LEN] = {0};
+ char str[STR_LEN] = {0};
+
+ while (fgets(buf, MAX_LEN, infile) != NULL) {
+ if (sscanf(buf, FMT_STRING, str) == 1) {
+ // just a precaution, good 'ole "allocate x2 if it doesn't fit anymore"
+ if (numbers.count >= numbers.limit) {
+ numbers.limit *= 2;
+ numbers.data = reallocf(numbers.data, numbers.limit * sizeof(long));
+ if (numbers.data == NULL) {
+ PRINT_ERR(reallocf)
+ return -1;
+ }
+ }
+ numbers.data[numbers.count++] = strtol(str, NULL, 2);
+ bzero(buf, MAX_LEN);
+ bzero(str, STR_LEN);
+ }
+ }
+
+ long oxygen_number = 0;
+ long scrubber_number = 0;
+ struct numbers_t oxygen;
+ struct numbers_t scrubber;
+ init_numbers(&oxygen, 0);
+ init_numbers(&scrubber, 0);
+ if (!copy_numbers(&numbers, &oxygen) || !copy_numbers(&numbers, &scrubber)) {
+ fprintf(stderr, "copy_numbers() error\n");
+ return false;
+ }
+
+ for (int bit = BITS_COUNT - 1; bit >= 0; --bit) {
+ filter_numbers_by_bit(&oxygen, bit, compare_oxygen);
+ filter_numbers_by_bit(&scrubber, bit, compare_scrubber);
+ }
+
+ if (oxygen.count != 1 || scrubber.count != 1) {
+ fprintf(stderr, "Filter failed :C");
+ goto finish;
+ }
+
+ oxygen_number = oxygen.data[0];
+ scrubber_number = scrubber.data[0];
+
+ // mutiny! ignoring feof/ferror.
+finish:
+ free(numbers.data);
+ free(oxygen.data);
+ free(scrubber.data);
+ fclose(infile);
+
+ return oxygen_number * scrubber_number;
+}
+
+bool init_numbers(struct numbers_t *numbers, size_t limit) {
+ numbers->data = NULL;
+ numbers->count = 0;
+ numbers->limit = limit;
+
+ if (limit > 0) {
+ numbers->data = calloc(limit, sizeof(long));
+ if (numbers->data == NULL) {
+ PRINT_ERR(calloc)
+ return false;
+ }
+ }
+
+ return true;
+}
+
+bool copy_numbers(const struct numbers_t *src, struct numbers_t *dst) {
+ if (src->data == NULL || src->count == 0 || src->limit == 0)
+ return false;
+
+ size_t dst_size = src->count * sizeof(long);
+ dst->data = realloc(dst->data, dst_size);
+ dst->count = src->count;
+ dst->limit = src->limit;
+ memcpy(dst->data, src->data, dst_size);
+
+ return true;
+}
+
+void move_numbers(struct numbers_t *src, struct numbers_t *dst) {
+ free(dst->data);
+ dst->data = src->data;
+ dst->count = src->count;
+ dst->limit = src->limit;
+}
+
+bool filter_numbers_by_bit(struct numbers_t *numbers, int bit_num, bool (cmp)(size_t, size_t)) {
+ if (numbers->count == 1)
+ return false;
+
+ struct numbers_t filtered_0;
+ if (!init_numbers(&filtered_0, numbers->count))
+ return false;
+
+ struct numbers_t filtered_1;
+ if (!init_numbers(&filtered_1, numbers->count))
+ return false;
+
+ for (size_t i = 0; i < numbers->count; ++i) {
+ if (numbers->data[i] & (1 << bit_num)) {
+ filtered_1.data[filtered_1.count++] = numbers->data[i];
+ } else {
+ filtered_0.data[filtered_0.count++] = numbers->data[i];
+ }
+ }
+
+ if (cmp(filtered_0.count, filtered_1.count)) {
+ move_numbers(&filtered_0, numbers);
+ free(filtered_1.data);
+ } else {
+ move_numbers(&filtered_1, numbers);
+ free(filtered_0.data);
+ }
+
+ return true;
+}
