use same naming as clj solution

.clangd

@@ -0,0 +1,2 @@
+CompileFlags:
+  Add: [--std=c++23 ]

input/2025-4.sample.txt

@@ -0,0 +1,10 @@
+..@@.@@@@.
+@@@.@.@.@@
+@@@@@.@.@@
+@.@@@@..@.
+@@.@@@@.@@
+.@@@@@@@.@
+.@.@.@.@@@
+@.@@@.@@@@
+.@@@@@@@@.
+@.@.@@@.@.

input/2025-5.sample.txt

@@ -0,0 +1,11 @@
+3-5
+10-14
+16-20
+12-18
+
+1
+5
+8
+11
+17
+32

input/2025-6.sample.txt

@@ -0,0 +1,4 @@
+123 328  51 64 
+ 45 64  387 23 
+  6 98  215 314
+*   +   *   +  

input/2025-7.sample.txt

@@ -0,0 +1,16 @@
+.......S.......
+...............
+.......^.......
+...............
+......^.^......
+...............
+.....^.^.^.....
+...............
+....^.^...^....
+...............
+...^.^...^.^...
+...............
+..^...^.....^..
+...............
+.^.^.^.^.^...^.
+...............

script/async-build

@@ -0,0 +1,5 @@
+#!/bin/bash
+
+set -e
+
+script/build $1&

script/dbg

@@ -1,5 +1,5 @@
 #!/bin/bash
 
 set -e
-./build $1
+script/build $1
 gdb a.out

script/run

@@ -2,5 +2,5 @@
 
 set -e
 
-./build $1
+script/build $1
 ./a.out

src/day1.cpp

@@ -1,3 +1,4 @@
+// :autocmd BufWritePost *.cpp :silent exec "!script/async-build 1"
 #include <fstream>
 #include <iostream>
 #include <vector>

src/day2.cpp

@@ -1,4 +1,4 @@
-// :autocmd BufWritePost *.cpp :silent exec "!./build 2"
+// :autocmd BufWritePost *.cpp :silent exec "!script/async-build 2"
 #include <fstream>
 #include <iostream>
 #include <numeric>
@@ -24,6 +24,7 @@ int main() {
   }
   std::cout << "Part 1: " << part_1(v) << std::endl;
   std::cout << "Part 2: " << part_2(v) << std::endl;
+  return 0;
 }
 
 int64_t part_1(const std::vector<Data> &v) {
@@ -60,24 +61,10 @@ int64_t solve_n(int64_t n) {
 }
 
 int64_t part_2(const std::vector<Data> &v) {
-  int64_t ans{0};
+  return std::accumulate(v.begin(), v.end(), 0ll, [](int64_t acc, Data d) {
-  for (auto d : v) {
-    for (auto n{d.min}; n <= d.max; ++n) {
-      ans += solve_n(n);
-    }
-  }
-
-  // todo: dead code, delete me, then inline solve_n
-  int64_t foobar = std::accumulate(v.begin(), v.end(), 0, [&ans](int64_t acc, Data d) {
     for (auto n{d.min}; n <= d.max; ++n) {
       acc += solve_n(n);
     }
     return acc;
   });
-
-  // help please :)
-  // why ans != foobar? looks like same but not same
-  // stepping through with debugger, it even seems the same on last iteration of accumulate
-
-  return ans;
 }

src/day3.cpp

@@ -1,4 +1,4 @@
-// :autocmd BufWritePost *.cpp :silent exec "!./build 3"
+// :autocmd BufWritePost *.cpp :silent exec "!script/async-build 3"
 #include <fstream>
 #include <iostream>
 #include <numeric>
@@ -26,14 +26,15 @@ char get_max_char(std::string_view s) {
 }
 
 int64_t solve(const std::string_view line, size_t cnt_to_activate) {
-  const auto search{line.substr(0, line.size() - cnt_to_activate + 1)};
+  const std::string_view search{line.substr(0, line.size() - cnt_to_activate + 1)};
   const char max_char{get_max_char(search)}, null_terminator{'\0'};
-  const auto max_char_idx{search.find(&max_char, 0)};
+  const size_t max_char_idx{search.find(&max_char, 0)};
   const int64_t max_char_as_int = max_char - '0';
   if (cnt_to_activate == 1) {
     return max_char_as_int;
   }
-  const auto recur{solve(line.substr(max_char_idx + 1), cnt_to_activate - 1)};
+  const int64_t recur{solve(line.substr(max_char_idx + 1), cnt_to_activate - 1)};
+  // slightly hacky... integral concat better?
   return std::stoll(std::string(&max_char) + std::to_string(recur));
 }
 

src/day4.cpp

@@ -0,0 +1,97 @@
+// :autocmd BufWritePost *.cpp :silent exec "!script/async-build 4"
+#include <cstdint>
+#include <fstream>
+#include <iostream>
+#include <vector>
+#include <algorithm>
+
+// investigate nob.h and c macros, macroify derive(eq, hash, ...)
+struct Roll {
+  int64_t row;
+  int64_t col;
+};
+
+bool operator==(const Roll &lhs, const Roll &rhs) {
+  return lhs.row == rhs.row && lhs.col == rhs.col;
+}
+
+using Grid = std::vector<std::string>;
+using Rolls = std::vector<Roll>;
+
+int64_t part_1(const Grid &grid, const Rolls &rolls);
+int64_t part_2(Grid, std::vector<Roll> rolls);
+
+int main() {
+  std::ifstream file{"input/2025-4.txt"};
+  std::string line;
+  Roll roll_iter{};
+  std::vector<Roll> rolls;
+  Grid grid;
+  while (std::getline(file, line)) {
+    grid.push_back(line);
+    for (char c : line) {
+      if (c == '@') {
+        Roll local_copy = roll_iter;
+        rolls.push_back(local_copy);
+      }
+      roll_iter.col += 1;
+    }
+    roll_iter.row += 1;
+    roll_iter.col = 0;
+  }
+  std::cout << "Part 1: " << part_1(grid, rolls) << std::endl;
+  std::cout << "Part 2: " << part_2(grid, rolls) << std::endl;
+}
+
+void is_roll_helper(size_t row, size_t col, const Grid &grid, short &ans) {
+  if (row >= 0 && row < grid.size() && col >= 0 && col < grid[row].size() &&
+      grid[row][col] == '@') {
+    ans += 1;
+  }
+}
+
+short num_neighbors(const Grid &grid, const Roll &roll) {
+  short ans{0};
+  is_roll_helper(roll.row - 1, roll.col - 1, grid, ans);
+  is_roll_helper(roll.row - 1, roll.col, grid, ans);
+  is_roll_helper(roll.row - 1, roll.col + 1, grid, ans);
+  is_roll_helper(roll.row, roll.col - 1, grid, ans);
+  is_roll_helper(roll.row, roll.col + 1, grid, ans);
+  is_roll_helper(roll.row + 1, roll.col - 1, grid, ans);
+  is_roll_helper(roll.row + 1, roll.col, grid, ans);
+  is_roll_helper(roll.row + 1, roll.col + 1, grid, ans);
+  return ans;
+}
+
+int64_t part_1(const Grid &grid, const Rolls &rolls) {
+  int64_t ans{0};
+  for (auto roll : rolls) {
+    auto cnt{num_neighbors(grid, roll)};
+    if (cnt < 4) {
+      ans += 1;
+    }
+  }
+  return ans;
+}
+
+int64_t part_2(Grid grid, Rolls rolls) {
+  int64_t last_roll_cnt = INT64_MAX;
+  int64_t ans{0};
+  Rolls to_delete{};
+  do {
+    to_delete.clear();
+    for (auto roll : rolls) {
+      auto cnt{num_neighbors(grid, roll)};
+      if (cnt < 4) {
+        ans += 1;
+        to_delete.emplace_back(roll);
+      }
+    }
+
+    for (auto roll : to_delete) {
+      std::erase(rolls, roll);
+      grid[roll.row][roll.col] = '.';
+    }
+  } while (to_delete.size() != 0);
+  return ans;
+}

src/day5.cpp

@@ -0,0 +1,77 @@
+// :autocmd BufWritePost *.cpp :silent exec "!script/async-build 5"
+#include <algorithm>
+#include <cstdint>
+#include <fstream>
+#include <iostream>
+#include <string>
+#include <vector>
+
+struct Range {
+  int64_t min;
+  int64_t max;
+};
+
+constexpr int compare(const Range &a, const Range &b) {
+  if (a.min == b.min) {
+    return a.max < b.max;
+  }
+  return a.min < b.min;
+}
+
+using Ranges = std::vector<Range>;
+using Nums = std::vector<int64_t>;
+
+int64_t part_1(const Ranges &ranges, const Nums &nums);
+int64_t part_2(const Ranges &ranges, const Nums &nums);
+
+int main() {
+  std::ifstream file{"input/2025-5.txt"};
+  std::string line;
+
+  Ranges ranges;
+  char throwaway;
+  while (std::getline(file, line) && line != "") {
+    Range r{};
+    sscanf(line.c_str(), "%ld-%ld", &r.min, &r.max);
+    ranges.push_back(r);
+  }
+
+  int64_t num;
+  Nums nums{};
+  while (file >> num) {
+    nums.push_back(num);
+  }
+  std::sort(ranges.begin(), ranges.end(), compare);
+
+  std::cout << "Part 1: " << part_1(ranges, nums) << std::endl;
+  std::cout << "Part 2: " << part_2(ranges, nums) << std::endl;
+  return 0;
+}
+
+int64_t part_1(const Ranges &ranges, const Nums &nums) {
+  int64_t ans{};
+  for (auto num : nums) {
+    for (auto range : ranges) {
+      if (num >= range.min && num <= range.max) {
+        ans += 1;
+        break;
+      }
+    }
+  }
+  return ans;
+}
+
+int64_t part_2(const Ranges &ranges, const Nums &nums) {
+  int64_t ans{};
+  int64_t scanner{0};
+  for (auto range : ranges) {
+    if (scanner < range.min) {
+      ans += range.max - range.min + 1;
+      scanner = range.max;
+    } else if (scanner <= range.max) {
+      ans += range.max - scanner;
+      scanner = range.max;
+    }
+  }
+  return ans;
+}

src/day6.cpp

@@ -0,0 +1,102 @@
+// :autocmd BufWritePost *.cpp :silent exec "!script/async-build 6"
+#include <cstdint>
+#include <fstream>
+#include <iostream>
+#include <sstream>
+#include <string>
+#include <vector>
+
+using Grid = std::vector<std::string>;
+using Ops = std::vector<char>;
+
+int64_t part_1(const Grid &grid, const Ops &ops);
+int64_t part_2(const Grid &grid, const Ops &ops);
+
+int main() {
+  Grid grid;
+  std::string line;
+  std::ifstream file{"input/2025-6.txt"};
+  size_t row{0};
+  while (std::getline(file, line)) {
+    grid.emplace_back(line);
+    row += 1;
+  }
+  auto op_line{grid[grid.size() - 1]};
+  std::istringstream reader{op_line};
+  char op;
+  std::vector<char> ops;
+  while (reader >> op) {
+    ops.push_back(op);
+  }
+  std::cout << part_1(grid, ops) << std::endl;
+  std::cout << part_2(grid, ops) << std::endl;
+  return 0;
+}
+
+int64_t part_1(const Grid &grid, const Ops &ops) {
+  std::vector<std::vector<int64_t>> blocks;
+  for (auto i{0}; i < grid.size() - 1; ++i) {
+    std::vector<int64_t> current_line{};
+    auto line = grid[i];
+    std::istringstream reader{line};
+    int64_t num;
+    while (reader >> num) {
+      current_line.push_back(num);
+    }
+    blocks.emplace_back(current_line);
+  }
+  int64_t ans{0};
+  for (int64_t i{0}; i < blocks[0].size(); ++i) {
+    if (ops[i] == '*') {
+      int64_t curr{1};
+      for (int64_t j{0}; j < blocks.size(); ++j) {
+        curr *= blocks[j][i];
+      }
+      ans += curr;
+    } else {
+      int64_t curr{0};
+      for (int64_t j{0}; j < blocks.size(); ++j) {
+        curr += blocks[j][i];
+      }
+      ans += curr;
+    }
+  }
+  return ans;
+}
+
+int64_t part_2(const Grid &grid, const Ops &ops) {
+  size_t op_iter{};
+  uint64_t ans{};
+  std::vector<int64_t> block;
+  for (size_t col{}; col < grid[0].length(); ++col) {
+    std::string col_str{""};
+    for (size_t row{}; row < grid.size() - 1; ++row) {
+      char c{grid[row][col]};
+      if (c >= '0' && c <= '9') {
+        col_str += c;
+      }
+    }
+    if (col_str == "") {
+      if (ops[op_iter] == '*') {
+        int64_t temp{1};
+        for (auto n : block) {
+          temp *= n;
+        }
+        ans += temp;
+      } else {
+        auto temp{0};
+        for (auto n : block) {
+          temp += n;
+        }
+        ans += temp;
+      }
+      block.clear();
+      ++op_iter;
+      continue;
+    } else {
+      int64_t num{std::stoll(col_str)};
+      block.push_back(num);
+    }
+  }
+  return ans;
+}

src/day7.cpp

@@ -0,0 +1,98 @@
+// :autocmd BufWritePost *.cpp :silent exec "!script/async-build 7"
+#include <algorithm>
+#include <cstdint>
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <numeric>
+#include <ranges>
+#include <set>
+#include <string>
+#include <utility>
+#include <vector>
+
+using Grid = std::vector<std::string>;
+using Location = std::tuple<size_t, size_t>;
+
+uint64_t part_1(const Grid &grid);
+uint64_t part_2(const Grid &grid);
+
+int main() {
+  Grid grid;
+  std::ifstream file{"input/2025-7.txt"};
+  std::string line;
+  while (std::getline(file, line)) {
+    grid.emplace_back(line);
+  }
+  std::cout << "Part 1: " << part_1(grid) << std::endl;
+  std::cout << "Part 2: " << part_2(grid) << std::endl;
+  return 0;
+}
+
+char at_loc(const Grid &grid, size_t row, size_t col) {
+  if (row >= 0 && row < grid.size() && col >= 0 && col < grid[row].size()) {
+    return grid[row][col];
+  } else {
+    return '.';
+  }
+}
+
+Location find_start(const Grid &grid) {
+  const auto col{grid[0].find_first_of('S')};
+  if (col != std::string::npos) {
+    return {0, col};
+  } else {
+    std::unreachable();
+  }
+}
+
+uint64_t part_1(const Grid &grid) {
+  uint64_t ans{0};
+  Location start{find_start(grid)};
+  const auto [start_row, start_col]{start};
+  std::set<size_t> cols{};
+  cols.insert(start_col);
+  for (size_t row{start_row}; row < grid.size(); ++row) {
+    std::set<size_t> next_cols{};
+    for (auto col : cols) {
+      if (at_loc(grid, row, col) == '^') {
+        ans += 1;
+        next_cols.insert(col + 1);
+        next_cols.insert(col - 1);
+      } else {
+        next_cols.insert(col);
+      }
+    }
+    cols = next_cols;
+  }
+  return ans;
+}
+
+void insert_or_increment(std::map<size_t, uint64_t> &cols, size_t col,
+                         uint64_t value) {
+  cols.insert({col, 0}).first->second += value;
+}
+
+uint64_t part_2(const Grid &grid) {
+  Location start = find_start(grid);
+  const auto [start_row, start_col]{start};
+  using namespace std::ranges;
+  auto view = iota_view{start_row, grid.size()};
+  std::map<size_t, uint64_t> starting_cols{{start_col, 1}};
+  auto cols = fold_left(view, starting_cols, [&grid](auto cols, auto row) {
+    return fold_left(cols, std::map<size_t, uint64_t>{},
+                     [&grid, &row](auto next_cols, auto col_cnt) {
+                       auto [col, cnt] = col_cnt;
+                       if (at_loc(grid, row, col) == '^') {
+                         insert_or_increment(next_cols, col - 1, cnt);
+                         insert_or_increment(next_cols, col + 1, cnt);
+                       } else {
+                         insert_or_increment(next_cols, col, cnt);
+                       }
+                       return next_cols;
+                     });
+  });
+  return fold_left(cols, 0ull, [](const uint64_t acc, const auto &entry) {
+    return acc + entry.second;
+  });
+}