Solve day 6 part 1

1 files changed, 40 insertions, 0 deletions

diff --git a/2019/day06.c b/2019/day06.c
new file mode 100644
index 0000000..fbfda57
--- /dev/null
+++ b/2019/day06.c
@@ -0,0 +1,40 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+static struct Node {
+	char name[4];
+	size_t parent;
+} tree[2048];
+
+static size_t node(const char *name) {
+	size_t i;
+	for (i = 0; tree[i].name[0]; ++i) {
+		if (strcmp(name, tree[i].name)) continue;
+		return i;
+	}
+	strncpy(tree[i].name, name, sizeof(tree[i].name));
+	return i;
+}
+
+static size_t ancestors(size_t i) {
+	size_t n = 0;
+	while (i) {
+		i = tree[i].parent;
+		n++;
+	}
+	return n;
+}
+
+int main(void) {
+	node("COM");
+	char parent[4], child[4];
+	while (EOF != scanf("%3s)%3s\n", parent, child)) {
+		tree[node(child)].parent = node(parent);
+	}
+	size_t orbits = 0;
+	for (size_t i = 0; tree[i].name[0]; ++i) {
+		orbits += ancestors(i);
+	}
+	printf("%zu\n", orbits);
+}