Make Grid iterable

2019/10.cpp

@@ -70,23 +70,23 @@ auto ClearView(Grid const& grid, Coord src, Coord dst) -> bool {
 auto Part1(Grid const& grid) {
   std::size_t best = 0;
   Coord base {};
-  grid.each([&](Coord src, char s) {
+  for (auto [src, s] : grid) {
     if ('#' == s) {
       std::size_t visible = 0;
-      grid.each([&](Coord dst, char d){
+      for (auto [dst, d] : grid) {
         if ('#' == d && src != dst) {
           if (ClearView(grid, src, dst)) {
             visible++;
           }
         }
-      });
+      }
       
       if (visible > best) {
         best = visible;
         base = src;
       }
     }
-  });
+  }
   return std::make_pair(best, base);
 }
 
@@ -94,11 +94,11 @@ auto Part2(Grid const& grid, Coord base, std::size_t n) {
   std::map<Rational<std::int64_t>, std::vector<Coord>> targets;
 
   // arrange all the other asteroids by their angle relative to the base
-  grid.each([&](Coord c, char v){
+  for (auto [c, v] : grid){
     if (c != base && v == '#') {
       targets[angle(c-base)].push_back(c);
     }
-  });
+  }
 
   // Sort to vectors per angle such that the nearest asteroids are at
   // the end of the list

2019/17.cpp

@@ -66,14 +66,14 @@ auto ComputePath(Grid const& grid)
 {
   // Determine starting location and direction
   Coord start{}, step{};
-  grid.each([&](Coord c, char v) {
+  for (auto [c, v] : grid) {
     switch (v) {
       case '^': start = c; step = { 0, -1}; break;
       case '>': start = c; step = { 0,  1}; break;
       case '<': start = c; step = {-1,  0}; break;
       case 'v': start = c; step = { 0,  1}; break;
     }
-  });
+  }
 
   auto is_path = [&](Coord c) {
     return grid.contains(c) && grid[c] == '#';

2019/18.cpp

@@ -41,11 +41,11 @@ auto SetKey(Doors& doors, char key) {
 
 auto FindFeatures(Grid const& grid) -> Features {
   Features features;
-  grid.each([&](Coord c, char v) {
+  for (auto [c, v] : grid) {
     if ('#' != v && '.' != v) {
       features[v] = c;
     }
-  });
+  }
   return features;
 }
 

2019/24.cpp

@@ -27,9 +27,9 @@ auto FindBugs(Grid const& grid) -> std::vector<Coord> {
   std::int64_t w = grid.Cols();
   std::int64_t h = grid.Rows();
 
-  grid.each([&](Coord c, char v) {
+  for (auto [c, v] : grid) {
     if (v == '#') result.push_back(c);
-  });
+  }
   return result;
 }