2024 day 18

2024/17/main-1.cpp

@@ -0,0 +1,80 @@
+#include "../../include/aoc.hpp"
+#include <bits/stdc++.h>
+using namespace std;
+
+int main() {
+	ios::sync_with_stdio(0);
+	cin.tie(0);
+
+	int ra, rb, rc;
+	cin.ignore(12);
+	cin >> ra;
+	cin.ignore(13);
+	cin >> rb;
+	cin.ignore(13);
+	cin >> rc;
+	cin.ignore(11);
+	vector<int> tape;
+	int n;
+	while (cin >> n) {
+		tape.push_back(n);
+		cin.ignore();
+	}
+
+	vector<int> out;
+	int p = 0;
+	while (p < tape.size() - 1) {
+		int opc = tape[p], opr = tape[p + 1], combo;
+		switch (opr) {
+		case 4:
+			combo = ra;
+			break;
+		case 5:
+			combo = rb;
+			break;
+		case 6:
+			combo = rc;
+			break;
+		default:
+			combo = opr;
+		}
+		switch (opc) {
+		case 0:
+			ra >>= combo;
+			break;
+		case 1:
+			rb ^= opr;
+			break;
+		case 2:
+			rb = combo & 7;
+			break;
+		case 3:
+			if (ra != 0) {
+				p = opr;
+				continue;
+			}
+			break;
+		case 4:
+			rb ^= rc;
+			break;
+		case 5:
+			out.push_back(combo & 7);
+			break;
+		case 6:
+			rb = ra >> combo;
+			break;
+		case 7:
+			rc = ra >> combo;
+			break;
+		}
+		p += 2;
+	}
+
+	if (out.size() > 0) {
+		cout << out[0];
+		for (int i = 1; i < out.size(); i++) {
+			cout << ',' << out[i];
+		}
+	}
+	cout << '\n';
+}

2024/17/main-2.cpp

@@ -0,0 +1,46 @@
+#include "../../include/aoc.hpp"
+#include <bits/stdc++.h>
+using namespace std;
+
+vector<int> tape;
+
+// HACK: hardcoded input
+ll rec(int i, ll a) {
+	for (ll aa = a; aa < a + 8; aa++) {
+		ll b = aa & 7;
+		b ^= 1;
+		ll c = aa >> b;
+		b ^= c ^ 4;
+		if ((b & 7) == tape[i]) {
+			if (i == 0) {
+				return aa;
+			} else {
+				ll n = rec(i - 1, aa << 3);
+				if (n != -1) {
+					return n;
+				}
+			}
+		}
+	}
+	return -1;
+}
+
+int main() {
+	ios::sync_with_stdio(0);
+	cin.tie(0);
+
+	int n;
+	cin.ignore(12);
+	cin >> n;
+	cin.ignore(13);
+	cin >> n;
+	cin.ignore(13);
+	cin >> n;
+	cin.ignore(11);
+	while (cin >> n) {
+		tape.push_back(n);
+		cin.ignore();
+	}
+
+	cout << rec(tape.size() - 1, 0) << '\n';
+}

2024/18/main.cpp

@@ -0,0 +1,58 @@
+#include "../../include/aoc.hpp"
+#include <bits/stdc++.h>
+using namespace std;
+
+unordered_map<icoord, int> m;
+const int smax = 70;
+
+void rec(icoord c, int score) {
+	if (!m.contains(c)) {
+		return;
+	}
+
+	int &s = m[c];
+	if (s != -1 && s <= score) {
+		return;
+	}
+
+	s = score;
+	score++;
+
+	rec(c + icoord(1, 0), score);
+	rec(c + icoord(-1, 0), score);
+	rec(c + icoord(0, 1), score);
+	rec(c + icoord(0, -1), score);
+}
+
+int main() {
+	ios::sync_with_stdio(0);
+	cin.tie(0);
+
+	string line;
+	bool inits[smax + 1][smax + 1] = {};
+	int i = 0;
+	while (getline(cin, line) && !line.empty()) {
+		// NOTE: found part 2 is just binary search on this number until you
+		// stop getting -1 as output
+		if (++i > 1024) {
+			break;
+		}
+		istringstream l(line);
+		int x, y;
+		l >> x;
+		l.ignore();
+		l >> y;
+		inits[x][y] = true;
+	}
+
+	for (int x = 0; x <= smax; x++) {
+		for (int y = 0; y <= smax; y++) {
+			if (!inits[x][y]) {
+				m[{x, y}] = -1;
+			}
+		}
+	}
+
+	rec({0, 0}, 0);
+	cout << m[{smax, smax}] << '\n';
+}