1 files changed, 69 insertions, 0 deletions
diff --git a/03/a.c b/03/a.c
new file mode 100644
index 0000000..caa1d60
--- /dev/null
+++ b/03/a.c
@@ -0,0 +1,69 @@
+#include <unistd.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#define BUF_SIZE 8192
+
+char buffer[BUF_SIZE];
+
+ssize_t read_to_buffer() {
+    ssize_t bytes = read(0, buffer, BUF_SIZE);
+    if (bytes < 0) {
+        printf("failed to read\n");
+        exit(1);
+    }
+    return bytes;
+}
+
+int tree(int position) {
+    if (buffer[position] == '.') {
+        return 0;
+    } else if (buffer[position] == '#') {
+        return 1;
+    } else {
+        printf("unknown character\n");
+        exit(1);
+    }
+}
+
+int file_position(int x, int y, int line_length) {
+    return (line_length + 2) * y + x;
+}
+
+int buffer_position(int x, int y, int line_length, int buffer_start) {
+    return file_position(x % line_length, y, line_length) - buffer_start;
+}
+
+int find_trees() {
+    int buffer_start = 0;
+    int line_length = 0;
+    int x = 0;
+    int y = 0;
+    ssize_t bytes = read_to_buffer();
+    int trees_hit = tree(0);
+
+    while (buffer[line_length] != '\r') {
+        line_length++;
+    }
+
+    int i = 2;
+    while (bytes) {
+        while (buffer_position(x + 3, y + 1, line_length, buffer_start) < bytes) {
+            y += 1;
+            x += 3;
+
+            trees_hit += tree(buffer_position(x, y, line_length, buffer_start));
+        }
+
+        buffer_start += bytes;
+        bytes = read_to_buffer();
+    }
+
+    return trees_hit;
+}
+
+int main() {
+    printf("%d\n", find_trees());
+}