1 files changed, 102 insertions, 0 deletions

diff --git a/2024/21/day21b.cpp b/2024/21/day21b.cpp
new file mode 100644
index 0000000..dcca14e
--- /dev/null
+++ b/2024/21/day21b.cpp
@@ -0,0 +1,102 @@
+#include <algorithm>
+#include <cstdint>
+#include <iostream>
+#include <limits>
+#include <map>
+#include <queue>
+#include <ranges>
+#include <set>
+#include <sstream>
+#include <string>
+#include <string_view>
+#include <vector>
+using namespace std;
+
+map<char, pair<int, int>> m_num = {
+        {'7', {0,0}}, {'8', {0,1}}, {'9', {0,2}},
+        {'4', {1,0}}, {'5', {1,1}}, {'6', {1,2}},
+        {'1', {2,0}}, {'2', {2,1}}, {'3', {2,2}},
+        {'x', {3,0}}, {'0', {3,1}}, {'A', {3,2}},
+};
+
+map<char, pair<int, int>> m_dir = {
+        {'x', {0,0}}, {'^', {0,1}}, {'A', {0,2}},
+        {'<', {1,0}}, {'v', {1,1}}, {'>', {1,2}},
+};
+
+map<pair<int, int>, char> rev_num;
+map<pair<int, int>, char> rev_dir;
+
+map<pair<char, char>, vector<string>> p;
+
+vector<pair<pair<int, int>, char>> directions = {
+        {{1,0}, 'v'}, {{-1,0}, '^'}, {{0,1}, '>'}, {{0,-1}, '<'}
+};
+
+int distance(int cx, int cy, int dx, int dy) {
+        return abs(cx-dx) + abs(cy-dy);
+}
+
+vector<string> paths(char c, char d,
+    map<char, pair<int, int>>& m, map<pair<int, int>, char>& rev) {
+        if (p[make_pair(c, d)].size() != 0) return p[make_pair(c, d)];
+        if (c == d) return {""};
+        if (c == 'x') return {};
+
+        vector<string> v;
+        auto [cx, cy] = m[c];
+        auto [dx, dy] = m[d];
+        for (auto [dir, dirc] : directions) {
+                pair i = make_pair(cx+dir.first, cy+dir.second);
+                if (distance(cx, cy, dx, dy) < distance(i.first, i.second, dx, dy))
+                        continue;
+                const auto next = paths(rev[i], d, m, rev);
+                for (auto n : next)
+                        v.push_back(dirc+n);
+        }
+
+        return p[make_pair(c, d)] = v;
+}
+
+map<tuple<char, char, int>, int64_t> t;
+int64_t pushes(char c, char d,
+    map<char, pair<int, int>>& m, map<pair<int, int>, char>& r, int n) {
+        if (t.count(make_tuple(c, d, n)))
+                return t[make_tuple(c, d, n)];
+        const auto p = paths(c, d, m, r);
+        auto ret = numeric_limits<int64_t>::max();
+        for (const auto& path : p) {
+                if (n == 0) {
+                        ret = min(ret, (int64_t)path.size()+1);
+                } else {
+                        string q = 'A' + path + 'A';
+                        int64_t u = 0;
+                        for (unsigned i = 0; i < q.size()-1; i++)
+                                u += pushes(q[i], q[i+1], m_dir, rev_dir, n-1);
+                        ret = min(ret, u);
+                }
+        }
+        return t[make_tuple(c, d, n)] = ret;
+}
+
+int64_t numeric(const string& code) {
+        return (code[0]-'0')*100 + (code[1]-'0')*10 + (code[2]-'0');
+}
+
+int main() {
+        for (auto [k, v] : m_num) rev_num[v] = k;
+        for (auto [k, v] : m_dir) rev_dir[v] = k;
+
+        string line;
+        int64_t tot = 0;
+        while (getline(cin, line)) {
+                int64_t comp = 0;
+                int64_t num = numeric(line);
+                line = 'A' + line;
+                for (unsigned i = 0; i < line.size()-1; i++)
+                        comp += pushes(line[i], line[i+1], m_num, rev_num, 25);
+                tot += comp * num;
+        }
+        cout << tot << endl;
+        return 0;
+}