Day 14 part 2 (WIP, too slow)

2019/day14.py

@@ -14,38 +14,64 @@ def main():
         input_tuples = [(int(q), n) for q, n in input_comps]
         transmos[result] = int(mult), input_tuples
 
-    print("Required ore for 1 FUEL:", get_required_ore(transmos, "FUEL", 1, {}))
+    # Part 1
+    ore_per_full = get_required_ore(transmos, "FUEL", 1, {})
+    print("Required ore for 1 FUEL:", ore_per_full)
 
-def get_required_ore(transmos, name, quantity, rabs):
+    # Part 2
+    # Input gives 397771 OPF.
+    # 10^12 ores with 13312 OPF example gives 82892753 FUEL.
+    # 10^12 ores with 180697 OPF example gives 5586022 FUEL.
+    # 10^12 ores with 2210736 OPF example gives 460664 FUEL.
+    # 10^12 / 82892753 / 13312 ~= 0.91
+    # 10^12 / 5586022 / 180697 ~= 0.99
+    # 10^12 / 460664 / 2210736 ~= 0.98
+    # Let's say our reaction will have this value at about 0.985.
+    # 10^12 / x / 397771 = 0.985  ->  x = 2552294
+    # Now on to our search.
+
+    fuel = 2552294
+    cursor = 10000
+    last_result = 0
+    min_target = 10**12 - ore_per_full
+    max_target = 10**12
+    was_below = False
+    was_above = False
+    while last_result not in range(min_target, max_target):
+        last_result = get_required_ore(transmos, "FUEL", fuel, {})
+        print("{} FUEL requires {} ORE.".format(fuel, last_result))
+        if last_result < min_target:
+            if was_above:
+                cursor /= 2
+            fuel += cursor
+        elif last_result > max_target:
+            if was_below:
+                cursor /= 2
+            fuel -= cursor
+    
+def get_required_ore(transmos, name, quantity, leftovers):
     if name == "ORE":
         return quantity
 
-    print("What is required for {} {}?".format(quantity, name))
     mult, comps = transmos[name]
     num_reactions = math.ceil(quantity / mult)
 
     created = 0
-    if name in rabs:
-        print("  Found {} in rab.".format(rabs[name]))
-        created += rabs[name]
-        rabs[name] = 0
+    if name in leftovers:
+        created += leftovers[name]
+        leftovers[name] = 0
 
     req_ore = 0
     for _ in range(num_reactions):
         if created >= quantity:
             break
-        print("  Creation of {} {}...".format(mult, name))
-        for rq, rn in comps:
-            req_ore += get_required_ore(transmos, rn, rq, rabs)
+        req_ore += sum(get_required_ore(transmos, rn, rq, leftovers) for rq, rn in comps)
         created += mult
-    print("  Possessing {} {}.".format(created, name))
 
     if created > quantity:
         leftover = created - quantity
-        rabs[name] = rabs.get(name, 0) + leftover
-        print("  Stored {} {} in rab.".format(leftover, name))
+        leftovers[name] = leftovers.get(name, 0) + leftover
     
-    print("Answer ({} {}): {} ores".format(quantity, name, req_ore))
     return req_ore