aoc 2015, day 19

1 files changed, 115 insertions, 0 deletions

diff --git a/2015/src/day19.cpp b/2015/src/day19.cpp
new file mode 100644
index 0000000..7801964
--- /dev/null
+++ b/2015/src/day19.cpp
@@ -0,0 +1,115 @@
+#include <algorithm>
+#include <cstddef>
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <set>
+#include <sstream>
+#include <string>
+#include <tuple>
+#include <vector>
+using namespace std;
+
+auto
+split(const string& line, char sep = ' ')
+{
+        vector<string> parts;
+        stringstream   input{ line };
+
+        for ( string part; getline(input, part, sep); ) {
+                parts.emplace_back(part);
+        }
+
+        return parts;
+}
+
+tuple<string, vector<tuple<string, string>>>
+read_file(string_view filename)
+{
+        fstream                       input{ filename };
+        vector<tuple<string, string>> table;
+        string                        molecule;
+
+        for ( string line; getline(input, line); ) {
+                auto parts = split(line);
+
+                if ( parts.size() == 3 && parts[1] == "=>" ) {
+                        table.emplace_back(parts[0], parts[2]);
+                }
+
+                if ( parts.size() == 1 ) {
+                        molecule = parts[0];
+                }
+        }
+        return { molecule, table };
+}
+
+void
+part1(const string& molecule, const vector<tuple<string, string>>& table)
+{
+        set<string> set;
+        for ( const auto& [left, right]: table ) {
+                size_t pos = 0;
+                while ( true ) {
+                        string temp = molecule;
+                        pos         = temp.find(left, pos);
+                        if ( pos == string::npos ) {
+                                break;
+                        }
+                        temp.replace(pos, left.length(), right);
+                        ++pos;
+
+                        set.insert(temp);
+                }
+        }
+        cout << set.size() << endl;
+}
+
+size_t
+replace_all(string& str, string_view replace, string_view replaceWith)
+{
+        size_t count = 0;
+        auto   pos   = str.find(replace);
+
+        while ( pos != string::npos ) {
+                str.replace(pos, replace.size(), replaceWith);
+                ++count;
+                pos = str.find(replace, pos + replace.size());
+        }
+
+        return count;
+}
+
+void
+part2(string molecule)
+{
+        replace_all(molecule, "Rn", "(");
+        replace_all(molecule, "Y", ",");
+        replace_all(molecule, "Ar", ")");
+
+        molecule.erase(remove_if(molecule.begin(), molecule.end(), [](auto chr) -> bool {
+                               return islower(chr);
+                       }),
+                       molecule.end());
+
+        transform(molecule.begin(), molecule.end(), molecule.begin(), [](auto chr) {
+                return isalpha(chr) ? 'X' : chr;
+        });
+
+        size_t count = 0;
+        while ( molecule != "X" ) {
+                for ( const auto& item: { "XX", "X(X)", "X(X,X)", "X(X,X,X)" } ) {
+                        count += replace_all(molecule, item, "X");
+                }
+        }
+
+        cout << count << endl;
+}
+
+int
+main()
+{
+        const auto [molecule, table] = read_file("data/day19.txt");
+        part1(molecule, table);
+        part2(molecule);
+}