use same naming as clj solution

.clangd

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

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};
-  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) {
+  return std::accumulate(v.begin(), v.end(), 0ll, [](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>

src/day4.cpp

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

src/day5.cpp

@@ -1,4 +1,4 @@
-// :autocmd BufWritePost *.cpp :silent exec "!./build 5"
+// :autocmd BufWritePost *.cpp :silent exec "!script/async-build 5"
 #include <algorithm>
 #include <cstdint>
 #include <fstream>

src/day6.cpp

@@ -1,4 +1,4 @@
-// :autocmd BufWritePost *.cpp :silent exec "!./build 6"
+// :autocmd BufWritePost *.cpp :silent exec "!script/async-build 6"
 #include <cstdint>
 #include <fstream>
 #include <iostream>

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;
+  });
+}