1 files changed, 70 insertions, 0 deletions
diff --git a/day07.cc b/day07.cc
new file mode 100644
index 0000000..e82162e
--- /dev/null
+++ b/day07.cc
@@ -0,0 +1,70 @@
+#include <algorithm>
+#include <iostream>
+#include <iterator>
+#include <numeric>
+#include <set>
+#include <sstream>
+#include <string>
+#include <map>
+#include <vector>
+
+using namespace std;
+
+map<string,int> weights;
+map<string,bool> onbottom;
+map<string,vector<string>> ontop;
+
+int weighing(string s) {
+	const auto &children = ontop[s];
+	vector<int> sw;
+
+	transform(begin(children), end(children), back_inserter(sw), weighing);
+
+	auto [min, max] = minmax_element(begin(sw), end(sw));
+	if (min != end(sw) && *min != *max) {
+		auto another = begin(sw);
+		while (another != end(sw) && (another == max || another == min))
+			another++;
+
+		auto wrong = *min == *another ? max : min;
+		auto wrongid = ontop[s][distance(sw.begin(), wrong)];
+
+		cout << weights[wrongid] + (*another - *wrong) << endl;
+		exit(0);  // lame
+	}
+
+	return accumulate(begin(sw), end(sw), weights[s]);
+}
+
+int
+main()
+{
+	string line;
+
+	while (getline(cin, line)) {
+		istringstream is1{line};
+		string name;
+		int weight;
+
+		is1 >> name; is1.ignore(5, '(');
+		is1 >> weight; is1.ignore(5, '>');
+
+		vector<string> v;
+		string item;
+
+		while (getline(is1, item, ',')) {
+			item.erase(0, 1);
+			v.push_back(item);
+			onbottom[item] = 1;
+		}
+
+		weights[name] = weight;
+		ontop[name] = v;
+	}
+
+	auto top = find_if_not(begin(weights), end(weights),
+	    [](auto v) { return onbottom.count(v.first); })->first;
+	
+	cout << top << "\n";
+	weighing(top);
+}