Rename shared packages by day instead of vaguely by purpose.

2018/internal/day07/construction.go

@@ -0,0 +1,54 @@
+package day07
+
+func SimulateConstruction(root *Node) int {
+	working := make(map[rune]*Node)
+	done := map[rune]bool{
+		0: true,
+	}
+	elapsed := 0
+
+	for {
+		// returns true when no work is left to do.
+		if tick(root, working, done) {
+			return elapsed
+		}
+
+		elapsed++
+	}
+}
+
+func tick(root *Node, working map[rune]*Node, done map[rune]bool) bool {
+	complete := true
+
+	// Find candidates, if we need new ones.
+	if len(working) < 5 {
+		candidates := findCandidates(root, done)
+		for _, candidate := range candidates {
+			if len(working) >= 5 {
+				break
+			}
+
+			// if we see a candidate that we can work on, put it in the map.
+			if working[candidate.Name] == nil {
+				working[candidate.Name] = candidate
+				complete = false
+			}
+		}
+	}
+
+	// work on each in-progress node.
+	for _, node := range working {
+		complete = false
+		node.Worked++
+
+		// if we're done, add it to done and delete from worker queue
+		// `-4` is exploiting the fact that the rune capital A is value
+		// 65 as an integer (and so on)
+		if node.Worked >= int(node.Name)-4 {
+			done[node.Name] = true
+			delete(working, node.Name)
+		}
+	}
+
+	return complete
+}