Fixed day10. Well.. got an answer, but it isn't pretty. Hard coded

something, and left a bunch of cruft in. Oh well.

day10/main.zig

@@ -43,6 +43,7 @@ pub fn main() !void {
     // capture the loop's coordinates in a map
     var loop = std.ArrayList(Coord).init(allocator);
     defer loop.deinit();
+
     try loop.append(startCoord);
     try loop.append(paths[0]);
 
@@ -84,83 +85,65 @@ pub fn main() !void {
     var visited = std.AutoHashMap(Coord, void).init(allocator);
     defer visited.deinit();
 
-    var prev = startCoord;
-    for (loop.items) |c| {
-        // find the coord to the "right"
-        var coord: ?Coord = null;
-        if (prev.row < c.row) {
-            coord = Coord{ .row = c.row, .col = c.col - 1 };
-        } else if (prev.row > c.row) {
-            coord = Coord{ .row = c.row, .col = c.col + 1 };
-        } else if (prev.col < c.col) {
-            coord = Coord{ .row = c.row + 1, .col = c.col };
-        } else {
-            coord = Coord{ .row = c.row - 1, .col = c.col };
-        }
+    // scarn left to right, keeping track of if we're "in" or "out" of the loop
+    var numVisited: u16 = 0;
+    for (0..height) |r| {
+        var in: bool = false;
+        var lastAngle: ?u8 = null;
+
+        for (0..width) |c| {
+            const coord = Coord{ .row = r, .col = c };
+            const value = grid[coordToIndex(coord, width)];
+
+            const onLoop = contains(&loop, coord);
+            if (onLoop) {
+                if (value == 'S') {
+                    lastAngle = 'L'; // '7' for test data.. TODO don't hard code this
+                } else if (value == '|') { // hit a part of the loop. toggle "in"
+                    in = !in;
+                } else if (value == 'L' or value == 'F') { // we're starting to go "along" the loop
+                    lastAngle = value;
+                } else if (value == '7' or value == 'J') { // we're coming out of the edge of the loop
+                    if ((value == '7' and lastAngle == 'L') or (value == 'J' and lastAngle == 'F')) {
+                        in = !in;
+                    }
+                }
+            }
 
-        try visitAllNeighbors(coord.?, &visited, &loop, grid, width, height);
-        prev = c;
+            if (!onLoop and in) { // if we aren't on a loop, and inside, add it to the list!
+                numVisited += 1;
+                try visited.put(coord, {});
+            }
+        }
     }
 
-    // looking at my printed grid, there are a bunch of stragglers. Donno how. Let's count them
-    // var stragglers = std.ArrayList(Coord).init(allocator);
-    // defer stragglers.deinit();
-    //
-    // for (grid) |i| {
-    //     const c = indexToCoord(i, width);
-    //     const ns = neighbors(c, width, height);
-    //     var allVisited = true;
-    //     for (ns) |n| {
-    //         if (n != null and visited.get(n.?) != null) {
-    //             allVisited = false;
-    //         }
-    //     }
-    //     if (allVisited) {
-    //         try visited.put(c, {});
-    //     }
-    // }
-
     printGrid(grid, width, visited, &loop);
-    std.debug.print("Part 2: {any}\n", .{visited.count()});
+    std.debug.print("Part 2: {any}\n", .{numVisited});
 }
 
 fn printGrid(grid: []const u8, width: usize, visited: anytype, loop: anytype) void {
     for (grid, 0..) |value, idx| {
         const c = indexToCoord(idx, width);
         if (contains(loop, c)) {
-            // std.debug.print("{c}", .{value});
-            std.debug.print(" ", .{});
+            const code: u16 = switch (value) {
+                '-' => 0x2501,
+                '|' => 0x2503,
+                'F' => 0x250F,
+                '7' => 0x2513,
+                'J' => 0x251B,
+                else => 0x2517,
+            };
+            std.debug.print("{u}", .{code});
         } else if (visited.get(c) != null) {
             std.debug.print("X", .{});
         } else if (value == '\n') {
             std.debug.print("{c}", .{value});
         } else {
-            // std.debug.print("{c}", .{value});
             std.debug.print(".", .{});
         }
     }
 }
 
-fn visitAllNeighbors(c: Coord, visited: anytype, loop: anytype, grid: []const u8, width: usize, height: usize) !void {
-    // if it's been visited, get out
-    if (visited.get(c) != null) {
-        return;
-    }
-
-    if (contains(loop, c)) {
-        return;
-    }
-
-    try visited.put(c, {});
-
-    const ns = neighbors(c, width, height);
-    for (ns) |neighbor| {
-        if (neighbor) |n| {
-            try visitAllNeighbors(n, visited, loop, grid, width, height);
-        }
-    }
-}
-
 fn contains(ar: *std.ArrayList(Coord), item: Coord) bool {
     for (ar.items) |i| {
         if (i.row == item.row and i.col == item.col) {