Day 5 - c++

2 files changed, 115 insertions, 1 deletions

diff --git a/README.md b/README.md
index a7ecc4a..3f77a72 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,8 @@
   - [Day 2](./day-2)
 - [x] Common LISP
   - [Day 3](./day-3)
-- [] C++
+- [x] C++
+  - [Day 4](./day-4)
 - [] Dart
 - [] Elixir
 - [] Emacs Lisp
diff --git a/day-04/sol.cpp b/day-04/sol.cpp
new file mode 100644
index 0000000..8c9569c
--- /dev/null
+++ b/day-04/sol.cpp
@@ -0,0 +1,113 @@
+#include <tuple>
+#include <iostream>
+#include <fstream>
+#include <string>
+#include <sstream>
+#include <stack>
+#include <cmath>
+#include <array>
+#include <algorithm>
+#include <cstdint>
+#include <vector>
+
+using stack_type = std::stack<char>;
+
+std::tuple<std::vector<stack_type>, int> build_stacks(std::vector<std::string> &lines)
+{
+  int num_stacks = std::ceil(lines[0].size() / 4.0);
+
+  std::vector<stack_type> stacks(num_stacks);
+
+  std::vector<int> stack_positions(num_stacks, 0);
+  int lines_of_stacks = 0;
+  for (std::string line : lines)
+  {
+    char l = '1';
+    for (int i = 0; i < line.size(); ++i)
+      if (line[i] == l)
+      {
+        stack_positions[l - '1'] = i;
+        l++;
+      }
+    if (l == num_stacks + '1')
+      break;
+    lines_of_stacks++;
+  }
+
+  for (int i = lines_of_stacks - 1; i >= 0; i--)
+    for (int j = 0; j < num_stacks; ++j)
+      if (lines[i][stack_positions[j]] != ' ')
+        stacks[j].push(lines[i][stack_positions[j]]);
+
+  return std::make_tuple(stacks, lines_of_stacks);
+}
+
+std::string solve1(std::vector<stack_type> &stacks, std::vector<std::string> &lines, int start_from)
+{
+  for (auto line = lines.begin() + start_from; line != lines.end(); ++line)
+  {
+    std::istringstream iss(*line);
+    std::string word;
+    int from = 0, to = 0, amount = 0;
+
+    while (iss >> word >> amount >> word >> from >> word >> to)
+      ;
+
+    for (int i = 0; i < amount; i++)
+    {
+      stacks[to - 1].push(stacks[from - 1].top());
+      stacks[from - 1].pop();
+    }
+  }
+
+  std::string result;
+  for (auto &stack : stacks)
+    result += stack.top();
+  return result;
+}
+
+std::string solve2(std::vector<stack_type> &stacks, std::vector<std::string> &lines, int start_from)
+{
+  stack_type curr;
+  for (auto line = lines.begin() + start_from; line != lines.end(); ++line)
+  {
+    std::istringstream iss(*line);
+    std::string word;
+    int from = 0, to = 0, amount = 0;
+
+    while (iss >> word >> amount >> word >> from >> word >> to)
+      ;
+
+    for (int i = 0; i < amount; i++)
+    {
+      curr.push(stacks[from - 1].top());
+      stacks[from - 1].pop();
+    }
+
+    for (int i = 0; i < amount; i++)
+    {
+      stacks[to - 1].push(curr.top());
+      curr.pop();
+    }
+  }
+
+  std::string result;
+  for (auto &stack : stacks)
+    result += stack.top();
+  return result;
+}
+
+int main()
+{
+  std::ifstream input("input");
+  std::vector<std::string> lines;
+  for (std::string line; std::getline(input, line);)
+    lines.push_back(line);
+
+  auto [stacks, start_from] = build_stacks(lines);
+  std::cout << "Solve 1: " << solve1(stacks, lines, start_from + 1) << std::endl;
+  auto [stacks2, start_from2] = build_stacks(lines);
+  std::cout << "Solve 2: " << solve2(stacks2, lines, start_from2 + 1) << std::endl;
+
+  return 0;
+}