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-rw-r--r--2020/11/part1.c123
-rw-r--r--2020/11/part2.c202
2 files changed, 325 insertions, 0 deletions
diff --git a/2020/11/part1.c b/2020/11/part1.c
new file mode 100644
index 0000000..459befe
--- /dev/null
+++ b/2020/11/part1.c
@@ -0,0 +1,123 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <malloc.h>
+#include <string.h>
+
+#define MAX_INPUT_WIDTH 128
+#define MAX_INPUT_HEIGTH 128
+#define MAX_INPUT MAX_INPUT_WIDTH * MAX_INPUT_HEIGTH
+
+int count_char(const char *source, char search)
+{
+ int oc = 0;
+ do {
+ oc += *source == search;
+ } while (*++source);
+
+ return oc;
+}
+
+void replace_char(char *destination, const char *source, char original, char replace)
+{
+ do {
+ if (*source == original) {
+ *destination = replace;
+ }
+ else {
+ *destination = *source;
+ }
+ } while (++destination && *++source);
+ *destination = 0;
+}
+
+int sur_oc_seats(const char *source, size_t width, size_t height, size_t index_y, size_t index_x)
+{
+ int num = 0;
+ // Check 3 seats on the line above
+ if (index_y > 0) {
+ size_t x = index_x == 0 ? index_x : index_x - 1;
+ size_t end_x = index_x < width - 1 ? index_x + 2 : index_x + 1;
+ for (; x < end_x; x++) {
+ num += source[(index_y - 1) * width + x] == '#';
+ }
+ }
+
+ // Check sides
+ if (index_x > 0) {
+ num += source[index_y * width + index_x - 1] == '#';
+ }
+
+ if (index_x < width - 1) {
+ num += source[index_y * width + index_x + 1] == '#';
+ }
+
+ // Check 3 seats on the line above
+ if (index_y < height - 1) {
+ size_t x = index_x == 0 ? index_x : index_x - 1;
+ size_t end_x = index_x < width - 1 ? index_x + 2 : index_x + 1;
+ for (; x < end_x; x++) {
+ num += source[(index_y + 1) * width + x] == '#';
+ }
+ }
+
+ return num;
+}
+
+int solve(const char *filename)
+{
+ FILE *file = fopen(filename, "r");
+
+ // Include space for newline and string terminator
+ char buffer[128] = { 0 };
+
+ char input[MAX_INPUT] = { 0 };
+ size_t height = 1;
+ fgets(buffer, 128, file);
+ size_t width = strchr(buffer, '\n') - buffer;
+ replace_char(input, buffer, 'L', '#');
+
+ while (fgets(buffer, 128, file)) {
+ // Round 1
+ replace_char(&input[height++ * width], buffer, 'L', '#');
+ }
+
+ fclose(file);
+
+ size_t size = height * width;
+
+ // Zero terminate
+ input[size] = 0;
+
+ char input2[MAX_INPUT] = { 0 };
+ do {
+ for (size_t i = 0; i < size; i++) {
+ if (input[i] == '.') {
+ input2[i] = '.';
+ }
+ else if (input[i] == 'L') {
+ if (sur_oc_seats(input, width, height, i / width, i % width) == 0) {
+ input2[i] = '#';
+ }
+ else {
+ input2[i] = 'L';
+ }
+ }
+ else if (input[i] == '#') {
+ if (sur_oc_seats(input, width, height, i / width, i % width) >= 4) {
+ input2[i] = 'L';
+ }
+ else {
+ input2[i] = '#';
+ }
+ }
+ }
+ } while (memcmp(input, input2, size) && memcpy(input, input2, size));
+
+ return count_char(input, '#');
+}
+
+int main(int argc, char *argv[])
+{
+ printf("%i\n", solve(argv[argc - 1]));
+}
diff --git a/2020/11/part2.c b/2020/11/part2.c
new file mode 100644
index 0000000..2443ddd
--- /dev/null
+++ b/2020/11/part2.c
@@ -0,0 +1,202 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <malloc.h>
+#include <string.h>
+
+#define MAX_INPUT_WIDTH 128
+#define MAX_INPUT_HEIGTH 128
+#define MAX_INPUT MAX_INPUT_WIDTH * MAX_INPUT_HEIGTH
+
+int count_char(const char *source, char search)
+{
+ int oc = 0;
+ do {
+ oc += *source == search;
+ } while (*++source);
+
+ return oc;
+}
+
+void replace_char(char *destination, const char *source, char original, char replace)
+{
+ do {
+ if (*source == original) {
+ *destination = replace;
+ }
+ else {
+ *destination = *source;
+ }
+ } while (++destination && *++source);
+ *destination = 0;
+}
+
+char get_char(const char *source, size_t width, size_t y, size_t x) {
+ return source[y * width + x];
+}
+
+int sur_oc_seats(const char *source, size_t width, size_t height, size_t index_y, size_t index_x)
+{
+ int num = 0;
+ // Check upwards
+ size_t y = index_y;
+ size_t x = index_x;
+ while (--y < height) {
+ char c = get_char(source, width, y, x);
+ if (c == '.') {
+ continue;
+ }
+
+ num += c == '#';
+ break;
+ }
+
+ // Check downwards
+ y = index_y;
+ while (++y < height) {
+ char c = get_char(source, width, y, x);
+ if (c == '.') {
+ continue;
+ }
+
+ num += c == '#';
+ break;
+ }
+
+ // Check left
+ y = index_y;
+ x = index_x;
+ while (--x < width) {
+ char c = get_char(source, width, y, x);
+ if (c == '.') {
+ continue;
+ }
+
+ num += c == '#';
+ break;
+ }
+
+ // Check right
+ x = index_x;
+ while (++x < width) {
+ char c = get_char(source, width, y, x);
+ if (c == '.') {
+ continue;
+ }
+
+ num += c == '#';
+ break;
+ }
+
+ // Check left upwards
+ y = index_y;
+ x = index_x;
+ while (--y < height && --x < width) {
+ char c = get_char(source, width, y, x);
+ if (c == '.') {
+ continue;
+ }
+
+ num += c == '#';
+ break;
+ }
+
+ // Check left downwards
+ y = index_y;
+ x = index_x;
+ while (++y < height && --x < width) {
+ char c = get_char(source, width, y, x);
+ if (c == '.') {
+ continue;
+ }
+
+ num += c == '#';
+ break;
+ }
+
+ // Check right upwards
+ y = index_y;
+ x = index_x;
+ while (--y < height && ++x < width) {
+ char c = get_char(source, width, y, x);
+ if (c == '.') {
+ continue;
+ }
+
+ num += c == '#';
+ break;
+ }
+
+ // Check right downwards
+ y = index_y;
+ x = index_x;
+ while (++y < height && ++x < width ) {
+ char c = get_char(source, width, y, x);
+ if (c == '.') {
+ continue;
+ }
+
+ num += c == '#';
+ break;
+ }
+
+ return num;
+}
+
+int solve(const char *filename)
+{
+ FILE *file = fopen(filename, "r");
+
+ // Include space for newline and string terminator
+ char buffer[128] = { 0 };
+
+ char input[MAX_INPUT] = { 0 };
+ size_t height = 1;
+ fgets(buffer, 128, file);
+ size_t width = strchr(buffer, '\n') - buffer;
+ replace_char(input, buffer, 'L', '#');
+
+ while (fgets(buffer, 128, file)) {
+ // Round 1
+ replace_char(&input[height++ * width], buffer, 'L', '#');
+ }
+
+ fclose(file);
+
+ size_t size = height * width;
+
+ // Zero terminate
+ input[size] = 0;
+
+ char input2[MAX_INPUT] = { 0 };
+ do {
+ for (size_t i = 0; i < size; i++) {
+ if (input[i] == '.') {
+ input2[i] = '.';
+ }
+ else if (input[i] == 'L') {
+ if (sur_oc_seats(input, width, height, i / width, i % width) == 0) {
+ input2[i] = '#';
+ }
+ else {
+ input2[i] = 'L';
+ }
+ }
+ else if (input[i] == '#') {
+ if (sur_oc_seats(input, width, height, i / width, i % width) >= 5) {
+ input2[i] = 'L';
+ }
+ else {
+ input2[i] = '#';
+ }
+ }
+ }
+ } while (memcmp(input, input2, size) && memcpy(input, input2, size));
+
+ return count_char(input, '#');
+}
+
+int main(int argc, char *argv[])
+{
+ printf("%i\n", solve(argv[argc - 1]));
+}
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