use same naming as clj solution

.clangd

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

src/day2.cpp

@@ -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) {
+  return std::accumulate(v.begin(), v.end(), 0ll, [](int64_t acc, Data d) {
     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);
+      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/day7.cpp

@@ -1,18 +1,21 @@
 // :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>;
 
-int64_t part_1(const Grid &grid);
-int64_t part_2(const Grid &grid);
+uint64_t part_1(const Grid &grid);
+uint64_t part_2(const Grid &grid);
 
 int main() {
   Grid grid;
@@ -35,19 +38,17 @@ char at_loc(const Grid &grid, size_t row, size_t col) {
 }
 
 Location find_start(const Grid &grid) {
-  for (int64_t row{0}; row < grid.size(); ++row) {
-    for (int64_t col{0}; col < grid[row].length(); ++col) {
-      if (grid[row][col] == 'S') {
-        return Location{row, col};
-      }
-    }
+  const auto col{grid[0].find_first_of('S')};
+  if (col != std::string::npos) {
+    return {0, col};
+  } else {
+    std::unreachable();
   }
-  throw "unreachable";
 }
 
-int64_t part_1(const Grid &grid) {
-  int64_t ans{0};
-  Location start = find_start(grid);
+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);
@@ -67,34 +68,31 @@ int64_t part_1(const Grid &grid) {
   return ans;
 }
 
-void insert_or_increment(std::map<size_t, int64_t> &cols, size_t col,
-                    int64_t value) {
-  auto iter = cols.find(col);
-  if (iter == cols.end()) {
-    cols.insert({col, value});
-  } else {
-    iter->second += value;
-  }
+void insert_or_increment(std::map<size_t, uint64_t> &cols, size_t col,
+                         uint64_t value) {
+  cols.insert({col, 0}).first->second += value;
 }
 
-int64_t part_2(const Grid &grid) {
+uint64_t part_2(const Grid &grid) {
   Location start = find_start(grid);
   const auto [start_row, start_col]{start};
-  std::map<size_t, int64_t> cols;
-  cols.insert(std::make_pair(start_col, 1));
-  for (size_t row{start_row}; row < grid.size(); ++row) {
-    std::map<size_t, int64_t> next_cols;
-    for (auto [col, cnt] : cols) {
-      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);
-      }
-    }
-    cols = std::move(next_cols);
-  }
-  return std::accumulate(
-      cols.begin(), cols.end(), 0ll,
-      [](int64_t acc, auto entry) { return acc + entry.second; });
+  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;
+  });
 }