4 files changed, 144 insertions, 0 deletions

diff --git a/2024/11/Makefile b/2024/11/Makefile
new file mode 100644
index 0000000..a5d27bb
--- /dev/null
+++ b/2024/11/Makefile
@@ -0,0 +1,24 @@
+CC=g++ -std=c++20 -g -Wall
+
+a:
+        ${CC} -o a.out day11a.cpp
+
+b:
+        ${CC} -o b.out day11b.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/2024/11/day11a.cpp b/2024/11/day11a.cpp
new file mode 100644
index 0000000..50c3ebf
--- /dev/null
+++ b/2024/11/day11a.cpp
@@ -0,0 +1,57 @@
+#include <algorithm>
+#include <cstdint>
+#include <iostream>
+#include <map>
+#include <ranges>
+#include <set>
+#include <sstream>
+#include <string>
+#include <string_view>
+#include <vector>
+using namespace std;
+
+pair<uint64_t, uint64_t> split(uint64_t a) {
+        int digits = 0;
+        for (uint64_t b = a; b != 0; b /= 10)
+                digits++;
+
+        if (digits % 2 == 1)
+                return make_pair(0, 0);
+
+        uint64_t j = 1;
+        for (int k = 0; k < digits/2; k++)
+                j *= 10;
+
+        return make_pair(a/j, a%j);
+}
+
+uint64_t count(uint64_t a, int n) {
+        if (n == 0)
+                return 1;
+
+        if (a == 0)
+                return count(1, n-1);
+
+        if (auto [x, y] = split(a); x != 0) {
+                auto c1 = count(x, n-1);
+                auto c2 = count(y, n-1);
+                return c1+c2;
+        }
+
+        return count(a*2024, n-1);
+}
+
+int main() {
+        uint64_t x;
+        vector<uint64_t> old, v;
+        while (cin >> x)
+                v.push_back(x);
+
+        uint64_t tot = 0;
+        for (auto a : v)
+                tot += count(a, 25);
+
+        cout << tot << endl;
+
+        return 0;
+}
diff --git a/2024/11/day11b.cpp b/2024/11/day11b.cpp
new file mode 100644
index 0000000..7f78e8e
--- /dev/null
+++ b/2024/11/day11b.cpp
@@ -0,0 +1,62 @@
+#include <algorithm>
+#include <cstdint>
+#include <iostream>
+#include <map>
+#include <ranges>
+#include <set>
+#include <sstream>
+#include <string>
+#include <string_view>
+#include <vector>
+using namespace std;
+
+map<pair<uint64_t, uint64_t>, uint64_t> t;
+
+pair<uint64_t, uint64_t> split(uint64_t a) {
+        int digits = 0;
+        for (uint64_t b = a; b != 0; b /= 10)
+                digits++;
+
+        if (digits % 2 == 1)
+                return make_pair(0, 0);
+
+        uint64_t j = 1;
+        for (int k = 0; k < digits/2; k++)
+                j *= 10;
+
+        return make_pair(a/j, a%j);
+}
+
+uint64_t count(uint64_t a, int n) {
+        if (n == 0)
+                return 1;
+
+        if (auto it = t.find(make_pair(a, n)); it != t.end())
+                return it->second;
+
+        if (a == 0)
+                return t[make_pair(a, n)] = count(1, n-1);
+
+        if (auto [x, y] = split(a); x != 0) {
+                auto c1 = count(x, n-1);
+                auto c2 = count(y, n-1);
+                return t[make_pair(a, n)] = c1+c2;
+        }
+
+        return t[make_pair(a, n)] = count(a*2024, n-1);
+}
+
+int main() {
+        uint64_t x;
+        vector<uint64_t> old, v;
+        while (cin >> x)
+                v.push_back(x);
+
+        uint64_t tot = 0;
+        for (auto a : v)
+                tot += count(a, 75);
+
+        cout << tot << endl;
+
+        return 0;
+}
diff --git a/2024/learned.txt b/2024/learned.txt
index 56fa515..440571a 100644
--- a/2024/learned.txt
+++ b/2024/learned.txt
@@ -8,3 +8,4 @@ List of things I learned (or refreshed) with this year's AoC.
 * Day 5: std::find and std::replace
 * Day 8: set::insert_range(), but it is from C++23 only
 * Day 9: std::views
+* Day 11: if(init; cond)