Advent of Code 2022 day 5

advent_of_code_2022/day5/main2.cc

@@ -0,0 +1,81 @@
+#include <fmt/format.h>
+#include <iostream>
+#include <vector>
+
+std::vector<std::vector<char>> read_initial_setup()
+{
+    std::string buffer;
+    std::vector<std::vector<char>> stacks;
+
+    while (true)
+    {
+        std::getline(std::cin, buffer);
+        if (buffer[1] == '1')
+            break;
+
+        for (std::size_t idx = 0; (1 + (4 * idx)) < buffer.size(); ++idx)
+        {
+            std::size_t crate = 1 + (4 * idx);
+            if (buffer[crate] != ' ')
+            {
+                if (stacks.size() <= idx)
+                    stacks.resize(idx + 1);
+                stacks[idx].push_back(buffer[crate]);
+            }
+        }
+    }
+
+    std::getline(std::cin, buffer); // read empty line
+
+    // flip them around, faster indexing
+    for (auto& stack : stacks)
+        stack = std::vector<char>{stack.rbegin(), stack.rend()};
+    
+    return stacks;
+};
+
+struct Instruction
+{
+    std::size_t move{};
+    std::size_t from{};
+    std::size_t to{};
+};
+
+Instruction read_instruction()
+{
+    Instruction instruction;
+    std::string buffer;
+    std::cin >> buffer; // read 'move'
+    std::cin >> instruction.move;
+    std::cin >> buffer; // 'from'
+    std::cin >> instruction.from;
+    std::cin >> buffer; // 'to'
+    std::cin >> instruction.to;
+    instruction.from -= 1;
+    instruction.to -= 1;
+    return instruction;
+}
+
+int main()
+{
+    auto stacks = read_initial_setup();
+
+    while (true)
+    {
+        auto instruction = read_instruction();
+        if (instruction.from == instruction.to)
+            continue;
+
+        auto begin = stacks[instruction.from].end() - instruction.move;
+        stacks[instruction.to].insert(stacks[instruction.to].end(), begin, stacks[instruction.from].end());
+        stacks[instruction.from].erase(begin, stacks[instruction.from].end());
+
+        if (std::cin.eof())
+            break;
+    }
+
+    fmt::print("Result: ");
+    for (const auto& stack : stacks)
+        fmt::print("{}", stack.back());
+    fmt::print("\n");
+}