5

Author: gogsbread

cpp/5.cpp

@@ -0,0 +1,81 @@
+#include "common.h"
+
+namespace {
+struct Move {
+  long qty;
+  long src;
+  long dst;
+};
+
+auto parse(const auto &input) {
+  enum class mode { stack, move };
+  mode m{mode::stack};
+  std::vector<std::deque<char>> sts(10);
+  std::vector<Move> mvs{};
+  for (const auto &l : input) {
+    if (l.empty()) {
+      m = mode::move;
+      continue;
+    }
+    if (l[1] == '1') {
+      continue;
+    }
+    if (m == mode::stack) {
+      for (size_t i = 1; i < l.size(); i += 4) {
+        if (l[i] != ' ')
+          sts[static_cast<int>(i / 4)].push_front(l[i]);
+      }
+    } else if (m == mode::move) {
+      Move mv{};
+      sscanf(l.c_str(), "move %ld from %ld to %ld", &mv.qty, &mv.src, &mv.dst);
+      --mv.src;
+      --mv.dst;
+      mvs.emplace_back(std::move(mv));
+    }
+  }
+  return std::move(make_tuple(sts, mvs));
+}
+
+std::string p1(const auto &input) {
+  auto [sts, mvs] = parse(input);
+  for (auto mv : mvs) {
+    while (mv.qty--) {
+      sts[mv.dst].push_back(sts[mv.src].back());
+      sts[mv.src].pop_back();
+    }
+  }
+  std::ostringstream out;
+  for (const auto &st : sts) {
+    if (st.size())
+      out << st.back();
+  }
+  return out.str();
+}
+
+std::string p2(const auto &input) {
+  auto [sts, mvs] = parse(input);
+  for (auto mv : mvs) {
+    std::stack<char> t;
+    while (mv.qty--) {
+      t.push(sts[mv.src].back());
+      sts[mv.src].pop_back();
+    }
+    while (t.size()) {
+      sts[mv.dst].push_back(t.top());
+      t.pop();
+    }
+  }
+  std::ostringstream out;
+  for (const auto &st : sts) {
+    if (st.size())
+      out << st.back();
+  }
+  return out.str();
+}
+} // namespace
+
+int main() {
+  const auto &input = gb::advent2021::readIn();
+  gb::advent2021::writeOut(p1(input));
+  gb::advent2021::writeOut(p2(input));
+}

cpp/meson.build

@@ -18,9 +18,9 @@ executable('4',
     '4.cpp',
     dependencies: [])
 
-# executable('5',
-#     '5.cpp',
-#     dependencies: [])
+executable('5',
+    '5.cpp',
+    dependencies: [])
 
 # executable('6',
 #     '6.cpp',