day 9, wren

d9-wren/main.wren

@@ -0,0 +1,95 @@
+import "aoc" for AoC
+
+class Pos {
+    construct new() {
+        _x = 0
+        _y = 0
+    }
+
+    x { _x }
+    y { _y }
+
+    touches(other) {
+        var dx = (_x - other.x).abs
+        var dy = (_y - other.y).abs
+
+        return dx <= 1 && dy <= 1
+    }
+
+    static movement(h, t) {
+        if(h.touches(t)) {
+            return ""
+        }
+
+        var dx = h.x - t.x
+        var dy = h.y - t.y
+
+        if(dx < 0 && dy < 0) {
+            return "LD"
+        }
+        if(dx < 0 && dy > 0) {
+            return "LU"
+        }
+        if(dx > 0 && dy < 0) {
+            return "RD"
+        }
+        if(dx > 0 && dy > 0) {
+            return "RU"
+        }
+        if(dx < 0 ) {
+            return "L"
+        }
+        if(dx > 0 ) {
+            return "R"
+        }
+        if(dy < 0 ) {
+            return "D"
+        }
+        if(dy > 0 ) {
+            return "U"
+        }
+    }
+
+    u() { _y = _y + 1 }
+    d() { _y = _y - 1 }
+    l() { _x = _x - 1 }
+    r() { _x = _x + 1 }
+
+    move(direction) {
+        for(c in direction) {
+            if(c == "U") this.u()
+            if(c == "D") this.d()
+            if(c == "L") this.l()
+            if(c == "R") this.r()
+        }
+    }
+
+    xy { _x.toString + "," + _y.toString }
+}
+
+var h = Pos.new()
+var t = Pos.new()
+
+var rope = []
+for(i in 0...10) { rope.add(Pos.new()) }
+
+var seen_p1 = {}
+var seen_p2 = {}
+
+for(line in AoC.input.split("\n").where {|l| l != ""}) {
+    var split = line.split(" ")
+    var direction = split[0]
+    var count = Num.fromString(split[1])
+    for(i in 0...count) {
+        h.move(direction)
+        t.move(Pos.movement(h, t))
+        seen_p1[t.xy] = true
+
+        rope[0].move(direction)
+        for(i in 1...10) { rope[i].move(Pos.movement(rope[i-1], rope[i])) }
+        seen_p2[rope[9].xy] = true
+    }
+}
+
+System.print(seen_p1.count)
+System.print(seen_p2.count)