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they see me foldin'

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This commit is contained in:
Adam Jeniski 2025-12-28 05:39:48 -10:00
parent 8ff89aa2c2
commit f16918d137
1 changed files with 19 additions and 16 deletions
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35
src/day7.cpp
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@ -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;
});
}