From f16918d137ce3e020e11838f960733502dbf7263 Mon Sep 17 00:00:00 2001
From: ajet <ajeniski4@gmail.com>
Date: Sun, 28 Dec 2025 05:39:48 -1000
Subject: [PATCH] they see me foldin'

---
 src/day7.cpp | 35 +++++++++++++++++++----------------
 1 file changed, 19 insertions(+), 16 deletions(-)

diff --git a/src/day7.cpp b/src/day7.cpp
index 83f366c..2945334 100644
--- a/src/day7.cpp
+++ b/src/day7.cpp
@@ -77,21 +77,24 @@ uint64_t part_2(const Grid &grid) {
   Location start = find_start(grid);
   const auto [start_row, start_col]{start};
   using namespace std::ranges::views;
-  auto view = std::ranges::iota_view{start_row, grid.size()};
+
+  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 = std::accumulate(view.begin(), view.end(), starting_cols, [&grid](auto acc, auto row){
-    std::map<size_t, uint64_t> next_cols;
-    for (auto [col, cnt] : acc) {
-      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 std::accumulate(
-      cols.begin(), cols.end(), 0ull,
-      [](const uint64_t acc, const auto &entry) { return acc + entry.second; });
+  auto cols = fold_left(view, starting_cols, [&grid](auto acc, auto row) {
+    return fold_left(acc, 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;
+  });
 }