Day 1 (part 2 linear runtime)

.idea/misc.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
-  <component name="ProjectRootManager" version="2" languageLevel="JDK_15" default="true" project-jdk-name="Python 3.6" project-jdk-type="Python SDK">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_15" default="true" project-jdk-name="Python 3.8" project-jdk-type="Python SDK">
     <output url="file://$PROJECT_DIR$/out" />
   </component>
 </project>

day01/part2.py

@@ -1,14 +1,33 @@
 import math
-from itertools import combinations
 
-items = [int(x.strip()) for x in open("input.txt")]
+items = (int(x.strip()) for x in open("input.txt"))
+values = {(2020, 3)}
+tree = dict()
 
-COUNT = 3
 
-for vals in combinations(items, COUNT):
-    if sum(vals) == 2020:
+def tree_up(idx, step=1, offset = 0):
+    print(idx, step)
+    next = tree[(idx, step)] if (idx, step) in tree else None
+    appendix = [] if next is None else tree_up(next+idx, step=step+1, offset=idx)
+    return [idx - offset] + appendix
+
+
+for item in items:
+    tmp_values = set(values)
+    for elem in values:
+        new = (elem[0] - item, elem[1]-1)
+        if new == (0, 0):
+            vals = tree_up(item)
             print("Found [{}]: Sum={}, Product={}".format(
                 ", ".join(map(str, vals)),
                 sum(vals),
                 math.prod(vals)
             ))
+            exit(0)
+        elif new[0] < 0 or new[1] < 0:
+            # target value too low or to many sums
+            continue
+        else:
+            tree[new] = item
+            tmp_values.add(new)
+    values = tmp_values

python-aoc-2020.iml

@@ -2,7 +2,7 @@
 <module type="WEB_MODULE" version="4">
   <component name="FacetManager">
     <facet type="Python" name="Python">
-      <configuration sdkName="Python 3.6" />
+      <configuration sdkName="Python 3.8" />
     </facet>
   </component>
   <component name="NewModuleRootManager" inherit-compiler-output="true">
@@ -11,6 +11,6 @@
       <excludeFolder url="file://$MODULE_DIR$/venv" />
     </content>
     <orderEntry type="sourceFolder" forTests="false" />
-    <orderEntry type="library" name="Python 3.6 interpreter library" level="application" />
+    <orderEntry type="library" name="Python 3.8 interpreter library" level="application" />
   </component>
 </module>