Initial commit

2020/puzzle-14-02.cc

@@ -0,0 +1,93 @@
+#include <algorithm>
+#include <array>
+#include <cassert>
+#include <iostream>
+#include <list>
+#include <map>
+#include <regex>
+#include <string>
+
+using Data = std::uint64_t;
+using Mem = std::map<Data, Data>;
+
+struct Computer {
+
+  void add_instruction(std::string const &s) {
+    static const std::regex re("mem\\[(\\d+)\\] = (\\d+)");
+    std::smatch m;
+
+    if (s.substr(0, 4) == "mask") {
+      std::string mask = s.substr(7);
+      std::reverse(mask.begin(), mask.end());
+      set_ = 0;
+      bits_.clear();
+      std::size_t bit = 0;
+      std::cout << "Bitmask: floating bits: ";
+      for (auto c : mask) {
+        if (c == '1') {
+          set_ |= Data(1) << bit;
+
+        } else if (c == 'X') {
+          bits_.push_back(std::size_t(1) << bit);
+          std::cout << bit << " (" << (std::size_t(1) << bit) << ") ";
+
+        } else {
+          assert(c == '0');
+        }
+        ++bit;
+      }
+      assert(bit == mask.size());
+      std::cout << " set: 0x" << std::hex << set_ << std::dec << "\n";
+    } else if (std::regex_search(s, m, re)) {
+      Data loc = std::stoul(m.str(1));
+      Data value = std::stoul(m.str(2));
+      set_mem(loc, value);
+    }
+  }
+
+  void set_mem(Data loc, Data value) {
+    std::cout << "Writing: " << value << " to base loc " << std::hex << loc
+              << " which floats to:";
+    for (auto b : bits_) {
+      loc &= ~b;
+    }
+    for (std::size_t i = 0; i < (1 << bits_.size()); ++i) {
+      auto l = loc | set_;
+      for (std::size_t j = 0; j < bits_.size(); ++j) {
+        if (i & (std::size_t(1) << j)) {
+          l |= bits_[j];
+        }
+      }
+      std::cout << " " << l;
+      auto [it, success] = mem_.insert({l, value});
+      if (!success) {
+        it->second = value;
+      }
+    }
+    std::cout << std::dec << "\n";
+  }
+
+  Data mem_sum() const noexcept {
+    Data r = 0;
+    for (auto v : mem_) {
+      r += v.second;
+    }
+    return r;
+  }
+
+  Data set_;
+  std::vector<std::size_t> bits_;
+  Mem mem_;
+};
+
+int main(int argc, char **argv) {
+  Computer c;
+
+  std::string line;
+  while (std::getline(std::cin, line)) {
+    c.add_instruction(line);
+  }
+
+  std::cout << "Memory sum: " << std::dec << c.mem_sum() << "\n";
+  return 0;
+}