Add day 6

1 files changed, 44 insertions, 0 deletions

diff --git a/6/part2.c b/6/part2.c
new file mode 100644
index 0000000..11c8469
--- /dev/null
+++ b/6/part2.c
@@ -0,0 +1,44 @@
+#include <stdio.h>
+
+int plane_count(const char *filename)
+{
+    FILE *file = fopen(filename, "r");
+
+    // Include space for newline and string terminator
+    char buffer[32] = { 0 };
+
+    int tot = 0;
+    unsigned int current = 0xffffffff;
+
+    while (fgets(buffer, 32, file)) {
+        if (buffer[0] == '\n') {
+            if (current != 0xffffffff) {
+                tot += __builtin_popcount(current);
+                current = 0xffffffff;
+            }
+
+            continue;
+        }
+
+        unsigned int tmp = 0;
+        char *p = buffer;
+        do {
+            tmp |= 1 << (*p - 97);
+        } while (*++p != '\n');
+
+        current &= tmp;
+    }
+
+    fclose(file);
+
+    if (current != 0xffffffff) {
+        tot += __builtin_popcount(current);
+    }
+
+    return tot;
+}
+
+int main(int argc, char *argv[])
+{
+    printf("%i\n", plane_count(argv[argc - 1]));
+}