day[04]: simplified the solutions

src/04/solution.cxx

···
 #include <filesystem>
 #include <fstream>
 #include <print>
+#include <span>
 #include <sstream>
 #include <string>
 #include <vector>
···
   std::vector<std::string> data{};
 };
 
-unsigned int count_removable_rolls(Matrix &data) {
-  auto out = 0;
+struct Roll {
+  unsigned long row;
+  unsigned long col;
+};
+
+std::vector<Roll> get_removable_rolls(Matrix &data) {
+  std::vector<Roll> rolls{};
   for (unsigned long row = 0; row < data.height(); ++row) {
     for (unsigned long col = 0; col < data.width(); ++col) {
       if (data[row][col] != '@') {
-        std::print("{}", data[row][col]);
         continue;
       }
 
···
         }
       }
       if (count >= 4) {
-        std::print("{}", data[row][col]);
         continue;
       }
-      std::print("x");
-      out += 1;
+      auto roll = Roll {
+        .row = row,
+        .col = col,
+      };
+      rolls.push_back(roll);
     }
-    std::println();
   }
 
-  return out;
+  return rolls;
 }
 
-int remove_rolls(Matrix& data) {
-  auto removed = 0;
-
-  for (unsigned long row = 0; row < data.height(); ++row) {
-    for (unsigned long col = 0; col < data.width(); ++col) {
-      if (data[row][col] != '@') {
-        continue;
-      }
-
-      auto sur = data.get_surrounding(row, col);
-      int count = 0;
-      for (auto var : sur) {
-        if (var == '@') {
-          count += 1;
-        }
-      }
-      if (count >= 4) {
-        continue;
-      }
-      data.set(row, col, '.');
-      removed += 1;
-    }
+int remove_rolls(Matrix &data, std::span<Roll> removables) {
+  for (auto roll : removables) {
+    data.set(roll.row, roll.col, '.');
   }
 
-  return removed;
+  return removables.size();
 }
 
 int main() {
···
   file.read(input.data(), input_size);
 
   Matrix data(input);
+  auto removables = get_removable_rolls(data);
 
-  long long password_part_1 = count_removable_rolls(data);
+  long long password_part_1 = removables.size();
   long long password_part_2 = 0;
 
-  auto removables = count_removable_rolls(data);
-  while (removables > 0) {
-    std::println();
+  while (removables.size() > 0) {
+    password_part_2 += removables.size();
+    remove_rolls(data, removables);
 
-    password_part_2 += remove_rolls(data);
-    
-    removables = count_removable_rolls(data);
+    removables = get_removable_rolls(data);
   }
 
   std::println("Eureka! {} / {}", password_part_1, password_part_2);