Day 3.2

03/src/main.zig

@@ -5,6 +5,7 @@ const Error = error{ParseError};
 const Point = struct {
     X: i32,
     Y: i32,
+    Steps: i32, // number of steps taken to reach this point
 };
 
 const Points = std.ArrayList(Point);
@@ -44,48 +45,52 @@ const Step = struct {
 
 const World = struct {
     entries: Points,
-    pos: Point,
+    ticks: i32,
+    x: i32,
+    y: i32,
 
-    pub fn step(self: *World, in: Step) anyerror!void {
-        std.debug.warn("Step: {}\n", in);
+    pub fn step(self: *World, in: Step) void {
+        std.debug.warn("Step {}: {}\n", self.ticks, in);
 
+        var i: i32 = 0;
         switch (in.d) {
             .Up => {
-                try self.lineY(self.pos.Y - in.l, self.pos.Y - 1);
-                self.pos.Y -= in.l;
+                while (i < in.l) : (i += 1) {
+                    self.y -= 1;
+                    self.fill();
+                }
             },
             .Down => {
-                try self.lineY(self.pos.Y + 1, self.pos.Y + in.l);
-                self.pos.Y += in.l;
+                while (i < in.l) : (i += 1) {
+                    self.y += 1;
+                    self.fill();
+                }
             },
             .Left => {
-                try self.lineX(self.pos.X - in.l, self.pos.X - 1);
-                self.pos.X -= in.l;
+                while (i < in.l) : (i += 1) {
+                    self.x -= 1;
+                    self.fill();
+                }
             },
             .Right => {
-                try self.lineX(self.pos.X + 1, self.pos.X + in.l);
-                self.pos.X += in.l;
+                while (i < in.l) : (i += 1) {
+                    self.x += 1;
+                    self.fill();
+                }
             },
         }
     }
 
-    fn lineX(self: *World, start: i32, end: i32) anyerror!void {
-        var x: i32 = start;
-        while (x <= end) : (x += 1) {
-            try self.fill(x, self.pos.Y);
-        }
-    }
+    fn fill(self: *World) void {
+        self.ticks += 1;
 
-    fn lineY(self: *World, start: i32, end: i32) anyerror!void {
-        var y: i32 = start;
-        while (y <= end) : (y += 1) {
-            try self.fill(self.pos.X, y);
-        }
-    }
+        const point = Point{ .X = self.x, .Y = self.y, .Steps = self.ticks };
 
-    fn fill(self: *World, x: i32, y: i32) anyerror!void {
-        //self.entries = try self.alloc.realloc(self.entries, self.entries.len+1);
-        self.entries.appendAssumeCapacity(Point{ .X = x, .Y = y });
+        // TODO: use the lower number of ticks for multiple crossings
+        // I'm lucky, I don't need this.
+
+        std.debug.warn("\t{}\n", point);
+        self.entries.appendAssumeCapacity(point);
     }
 };
 
@@ -123,22 +128,26 @@ pub fn main() anyerror!void {
 
     var world: World = World{
         .entries = try Points.initCapacity(alloc, maxEntries),
-        .pos = Point{ .X = 0, .Y = 0 },
+        .ticks = 0,
+        .x = 0,
+        .y = 0,
     };
 
     // Line 1
     for (try getLine(stream)) |item| {
-        try world.step(item);
+        world.step(item);
     }
 
     // reset to origin
     const entriesA = world.entries;
     world.entries = try Points.initCapacity(alloc, maxEntries);
-    world.pos = Point{ .X = 0, .Y = 0 };
+    world.ticks = 0;
+    world.x = 0;
+    world.y = 0;
 
     // Line 2
     for (try getLine(stream)) |item| {
-        try world.step(item);
+        world.step(item);
     }
 
     const entriesB = world.entries;
@@ -148,7 +157,7 @@ pub fn main() anyerror!void {
     for (entriesA.toSlice()) |a| {
         for (entriesB.toSlice()) |b| {
             if (a.X == b.X and a.Y == b.Y) {
-                std.debug.warn("Match! {} => {}\n", a, manhattan(a.X, a.Y));
+                std.debug.warn("Match! {}, {} => {} : {}\n", a, b, manhattan(a.X, a.Y), a.Steps + b.Steps);
             }
         }
     }