2023 day 8

2023/8/main-1.cpp

@@ -0,0 +1,29 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+int main(void) {
+	ios::sync_with_stdio(0);
+	cin.tie(0);
+
+	string instructions;
+	getline(cin, instructions);
+	cin.ignore(1);
+
+	unordered_map<string, pair<string, string>> locs;
+
+	string line;
+	while (getline(cin, line)) {
+		locs[line.substr(0, 3)] = make_pair(line.substr(7, 3), line.substr(12, 3));
+	}
+
+	string current = "AAA";
+	int i = 0;
+	while (current != "ZZZ") {
+		if (instructions[i++ % instructions.length()] == 'L')
+			current = locs[current].first;
+		else
+			current = locs[current].second;
+	}
+
+	cout << i << '\n';
+}

2023/8/main-2.cpp

@@ -0,0 +1,54 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+int main(void) {
+	ios::sync_with_stdio(0);
+	cin.tie(0);
+
+	string instructions;
+	getline(cin, instructions);
+	cin.ignore(1);
+
+	unordered_map<string, pair<string, string>> locs;
+
+	string line;
+	while (getline(cin, line)) {
+		locs[line.substr(0, 3)] = make_pair(line.substr(7, 3), line.substr(12, 3));
+	}
+
+	vector<string> starts;
+
+	for (auto& loc : locs) {
+		if (loc.first[2] == 'A')
+			starts.push_back(loc.first);
+	}
+
+	unsigned long amounts[starts.size()];
+	memset(amounts, 0, starts.size() * sizeof(unsigned long));
+
+	long n = 0;
+	unsigned int done = starts.size();
+	while (done > 0) {
+		for (unsigned int i = 0; i < starts.size(); i++) {
+			if (amounts[i] != 0)
+				continue;
+
+			if (instructions[n % instructions.length()] == 'L')
+				starts[i] = locs[starts[i]].first;
+			else
+				starts[i] = locs[starts[i]].second;
+			if (starts[i][2] == 'Z') {
+				amounts[i] = n + 1;
+				done--;
+			}
+		}
+		n++;
+	}
+
+	unsigned long val = amounts[0];
+	for (unsigned int i = 1; i < starts.size(); i++) {
+		val = lcm(val, amounts[i]);
+	}
+
+	cout << val << '\n';
+}