Move all Advent of Codes into one repo

1 files changed, 37 insertions, 0 deletions

diff --git a/2020/03/part1.c b/2020/03/part1.c
new file mode 100644
index 0000000..b664b7d
--- /dev/null
+++ b/2020/03/part1.c
@@ -0,0 +1,37 @@
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define INC_RIGHT 3
+
+int count_trees(const char *filename)
+{
+    FILE *file = fopen(filename, "r");
+
+    // Include space for newline and string terminator
+    char buffer[64] = { 0 };
+    // Start is always safe
+    fgets(buffer, 64, file);
+    // strlen includes the newline
+    int width = strchr(buffer, '\n') - buffer;
+
+    int pos = INC_RIGHT;
+    int hit = 0;
+    while (fgets(buffer, 64, file)) {
+        if (buffer[pos] == '#') {
+            hit++;
+        }
+
+        pos = (pos + INC_RIGHT) % width;
+    }
+
+    fclose(file);
+
+    return hit;
+}
+
+int main(int argc, char *argv[])
+{
+    printf("%i", count_trees(argv[argc - 1]));
+}