Try out unordered_map for old problem

1 files changed, 69 insertions, 0 deletions

diff --git a/2024/11/day11b-hash.cpp b/2024/11/day11b-hash.cpp
new file mode 100644
index 0000000..e575512
--- /dev/null
+++ b/2024/11/day11b-hash.cpp
@@ -0,0 +1,69 @@
+#include <algorithm>
+#include <cstdint>
+#include <iostream>
+#include <unordered_map>
+#include <ranges>
+#include <set>
+#include <sstream>
+#include <string>
+#include <string_view>
+#include <vector>
+using namespace std;
+
+struct hash_pair {
+        template <class T1, class T2>
+        size_t operator()(const std::pair<T1, T2>& p) const {
+                return std::hash<T1>{}(p.first) ^ std::hash<T2>{}(p.second);
+        }
+};
+
+unordered_map<pair<uint64_t, uint64_t>, uint64_t, hash_pair> 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;
+}