5 files changed, 153 insertions, 0 deletions

diff --git a/2024/14/Makefile b/2024/14/Makefile
new file mode 100644
index 0000000..7f11c27
--- /dev/null
+++ b/2024/14/Makefile
@@ -0,0 +1,24 @@
+CC=g++ -std=c++20 -g -Wall
+
+a:
+        ${CC} -o a.out day14a.cpp
+
+b:
+        ${CC} -o b.out day14b.cpp
+
+clean:
+        rm -f a b
+
+atest: a
+        ./a.out
+
+btest: b
+        ./b.out
+
+arun: a
+        ./a.out < input
+
+brun: b
+        ./b.out < input
+
+.PHONY: a b clean atest btest arun brun
diff --git a/2024/14/clean.sh b/2024/14/clean.sh
new file mode 100755
index 0000000..ee99b15
--- /dev/null
+++ b/2024/14/clean.sh
@@ -0,0 +1,3 @@
+#!/bin/sh
+
+sed 's/p=//; s/v=//; s/,/ /g' 
diff --git a/2024/14/day14a.cpp b/2024/14/day14a.cpp
new file mode 100644
index 0000000..dff0ae9
--- /dev/null
+++ b/2024/14/day14a.cpp
@@ -0,0 +1,40 @@
+#include <algorithm>
+#include <cstdint>
+#include <iostream>
+#include <map>
+#include <ranges>
+#include <set>
+#include <sstream>
+#include <string>
+#include <string_view>
+#include <vector>
+using namespace std;
+
+#define N 101
+#define M 103
+#define T 100
+
+int quadrant(pair<int64_t, int64_t> p) {
+        if (p.first < N/2 && p.second < M/2)
+                return 1;
+        if (p.first < N/2 && p.second > M/2)
+                return 2;
+        if (p.first > N/2 && p.second < M/2)
+                return 3;
+        if (p.first > N/2 && p.second > M/2)
+                return 4;
+        return 0;
+}
+
+int main() {
+        string line;
+        int64_t p1, p2, v1, v2, q[5] = {0};
+        while (cin >> p1 >> p2 >> v1 >> v2) {
+                pair<int64_t, int64_t> final((p1 + T*(v1+N)) % N, (p2 + T*(v2+M)) % M);
+                q[quadrant(final)]++;
+        }
+
+        cout << q[1] * q[2] * q[3] * q[4] << endl;
+
+        return 0;
+}
diff --git a/2024/14/day14b.cpp b/2024/14/day14b.cpp
new file mode 100644
index 0000000..2402c0c
--- /dev/null
+++ b/2024/14/day14b.cpp
@@ -0,0 +1,85 @@
+/*
+I ran the simulation at 1FPS for a few minutes, staring at the screen and
+hoping to see a Christmas tree, without luck. But I noticed that the robots
+formed a strange "vertical" pattern every 103 timesteps, starting at t=30,
+and a strange "horizontal" pattern every 101 timesteps, starting at t=81.
+So I solved the diophantine equation 30+103y = 81+101x, and the smallest
+solution (y=76, x=77) gave the correct answer t=30+103*76=7858
+*/
+
+#include <algorithm>
+#include <cstdint>
+#include <iostream>
+#include <map>
+#include <ranges>
+#include <set>
+#include <sstream>
+#include <string>
+#include <string_view>
+#include <unistd.h>
+#include <vector>
+using namespace std;
+
+#define N 101
+#define M 103
+#define T 100
+
+char board[N][M];
+
+struct Robot {
+        pair<int64_t, int64_t> p, v;
+        Robot(int64_t p1, int64_t p2, int64_t v1, int64_t v2) : p(p1, p2), v(v1, v2) {}
+};
+
+int quadrant(pair<int64_t, int64_t> p) {
+        if (p.first < N/2 && p.second < M/2)
+                return 1;
+        if (p.first < N/2 && p.second > M/2)
+                return 2;
+        if (p.first > N/2 && p.second < M/2)
+                return 3;
+        if (p.first > N/2 && p.second > M/2)
+                return 4;
+        return 0;
+}
+
+pair<int64_t, int64_t> pos(Robot r, int64_t t) {
+        return make_pair((r.p.first + t*(r.v.first+N))%N,
+            (r.p.second + t*(r.v.second+M))%M);
+}
+
+void visualize(vector<Robot>& robots, int64_t t) {
+        for (int i = 0; i < N; i++)
+                for (int j = 0; j < M; j++)
+                        board[i][j] = ' ';
+        for (const auto& r : robots) {
+                auto [x,y] = pos(r, t);
+                board[x][y] = '*';
+        }
+        for (int i = 0; i < N; i++) {
+                for (int j = 0; j < M; j++)
+                        cout << board[i][j];
+                cout << endl;
+        }
+        cout << endl;
+}
+
+int main() {
+        string line;
+        int64_t p1, p2, v1, v2, q[5] = {0};
+        vector<Robot> r;
+        while (cin >> p1 >> p2 >> v1 >> v2)
+                r.push_back(Robot(p1, p2, v1, v2));
+
+
+        /* Starts at the solution */
+        for (int64_t t = 7858; ; t++) {
+                cout << "visualization of time " << t << ": " << endl;
+                sleep(1);
+                visualize(r, t);
+        }
+
+        cout << q[1] * q[2] * q[3] * q[4] << endl;
+
+        return 0;
+}
diff --git a/2024/template.cpp b/2024/template.cpp
index 2475ae7..e3fadb3 100644
--- a/2024/template.cpp
+++ b/2024/template.cpp
@@ -1,4 +1,5 @@
 #include <algorithm>
+#include <cstdint>
 #include <iostream>
 #include <map>
 #include <ranges>