Initial commit

2015/puzzle-19-01.cc

@@ -0,0 +1,47 @@
+#include <cassert>
+#include <cctype>
+#include <climits>
+#include <functional>
+#include <iostream>
+#include <map>
+#include <numeric>
+#include <regex>
+#include <set>
+#include <string>
+#include <variant>
+
+int main(int argc, char **argv) {
+  std::multimap<std::string, std::string> replacements;
+  bool collecting_replacements = true;
+  std::string line;
+  while (std::getline(std::cin, line)) {
+    if (line.empty()) {
+      collecting_replacements = false;
+    } else if (collecting_replacements) {
+      auto sep = line.find(" => ");
+      replacements.insert({line.substr(0, sep), line.substr(sep + 4)});
+    } else {
+      std::set<std::string> new_molecules;
+      for (unsigned pos = 0; pos < line.size(); ++pos) {
+        auto [it, ite] = replacements.equal_range(line.substr(pos, 1));
+        while (it != ite) {
+          new_molecules.insert(line.substr(0, pos) + it->second +
+                               line.substr(pos + 1));
+          ++it;
+        }
+        if (pos < line.size() - 1) {
+          auto [it, ite] = replacements.equal_range(line.substr(pos, 2));
+          while (it != ite) {
+            new_molecules.insert(line.substr(0, pos) + it->second +
+                                 line.substr(pos + 2));
+            ++it;
+          }
+        }
+      }
+      std::cout << line << "\n";
+      std::cout << "Solution: " << new_molecules.size() << "\n";
+    }
+  }
+
+  return 0;
+}