day 9 part 2

it seemed easier to go for a sparse implementation than try to make the
dense implementation from part 1 work

day09/sol.py

@@ -40,6 +40,46 @@ def solve(input):
         t += i*x
     print(t)
 
+def solve2(input):
+    freelist = []
+    blocks = {}
+    pos = 0
+    id = 0
+    for i in range(len(input)):
+        n = int(input[i])
+        if i % 2 == 0:
+            blocks[id] = (pos, n)
+            id += 1
+        else:
+            freelist.append((pos, n))
+        pos += n
+
+    lastid = id
+    for id in range(lastid-1,-1,-1):
+        bpos, blen = blocks[id]
+        for i in range(len(freelist)):
+            fpos, flen = freelist[i]
+            if bpos < fpos:
+                break
+            if blen <= flen:
+                blocks[id] = (fpos, blen)
+                if flen == blen:
+                    del freelist[i]
+                else:
+                    freelist[i] = (fpos+blen, flen-blen)
+                break
+
+    t = 0
+    for id in blocks:
+        i, n = blocks[id]
+        for x in range(i,i+n):
+            t += id*x
+
+    print(t)
+
 
 solve(sample)
 solve(input)
+
+solve2(sample)
+solve2(input)