From b8a8a2155f7bbe1e15fda9103713ba88fa902503 Mon Sep 17 00:00:00 2001
From: Danila Fedorin <danila.fedorin@gmail.com>
Date: Thu, 6 Dec 2018 22:52:33 -0800
Subject: [PATCH] Add solutions for day 7

---
 day7.cr | 87 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 87 insertions(+)
 create mode 100644 day7.cr

diff --git a/day7.cr b/day7.cr
new file mode 100644
index 0000000..8060dc5
--- /dev/null
+++ b/day7.cr
@@ -0,0 +1,87 @@
+require "./common.cr"
+
+lines = File.read("day7_input").split("\n")
+lines.pop
+
+REGEX = /Step (.+) must be finished before step (.+) can begin./
+
+all_children = {} of String => Set(String)
+all = Set(String).new
+finished = Set(String).new
+finished_array = Array(String).new
+
+lines.map(&.match(REGEX)).each do |match|
+  match = match.not_nil!
+  child = match[1]
+  parent = match[2]
+
+  all << child
+  all << parent
+  parent_set = all_children[parent]? || Set(String).new
+  parent_set << child
+  
+  all_children[parent] = parent_set
+end
+
+available_at = {} of String => Int32
+
+class String
+  def cost
+    return (self[0].bytes[0] - 'A'.bytes[0]).to_i32 + 1
+  end
+end
+
+def get_available(all, finished, children)
+  available = all.select do |it|
+    next false if finished.includes? it
+    next true unless set = children[it]?
+    next true if set.size == 0
+  end
+end
+
+children = all_children.clone
+while finished.size != all.size
+  available = get_available(all, finished, children)
+  available.sort!
+
+  first = available.first
+  finished << first
+  finished_array << first
+
+  children.values.each do |value|
+    value.delete first
+  end
+end
+puts finished_array.join ""
+
+finished.clear
+finished_array.clear
+children = all_children.clone
+workers = [0, 0, 0, 0, 0]
+current_time = 0
+finished_at = {} of String => Int32
+
+while finished.size < all.size
+  workers.each_with_index do |worker, index|
+    next if worker > current_time
+
+    current_finished = finished_at.select { |k, v| v <= current_time }.map(&.[0]).to_set
+    available = all.select do |it|
+      next false if finished.includes? it
+      next true unless nodes = children[it]?
+      (nodes - current_finished).size == 0
+    end
+    
+    available = available.sort!
+    next if available.empty?
+
+    first = available.first
+    finished_at[first] = current_time + first.cost + 60
+    workers[index] = current_time + first.cost + 60
+    finished_array << first
+    finished << first
+  end
+
+  current_time += 1
+end
+puts finished_at.values.max