day 2 part 2

day02/sol.py

@@ -12,11 +12,17 @@ def solve(input):
     t = 0
     for lo,hi in ranges:
         invalid = list(findinvalid(lo,hi))
-        if len(invalid) == 0:
+        #if len(invalid) == 0:
-            print(lo,hi,invalid)
+        #    print(lo,hi,invalid)
         t += sum(invalid)
     print(t)
 
+    t2 = 0
+    for lo,hi in ranges:
+        invalid2 = set(findinvalid2(lo,hi))
+        t2 += sum(invalid2)
+    print(t2)
+
 def findinvalid(lo, hi):
     assert len(str(hi)) - len(str(lo)) <= 1
     assert lo <= hi
@@ -36,5 +42,30 @@ def findinvalid(lo, hi):
                 #print(lo, hi, i,B,id)
                 yield id
 
+def findinvalid2(lo, hi):
+    assert lo <= hi,(lo,hi)
+    if len(str(hi)) != len(str(lo)):
+        assert len(str(hi)) - len(str(lo)) == 1
+        yield from findinvalid2(lo,10**len(str(lo))-1)
+        yield from findinvalid2(10**(len(str(hi))-1),hi)
+        return
+    N = len(str(hi))
+    for d in range(1,N):
+        if N%d == 0:
+            B = 10**d
+            BB = 10**(N-d)
+            factor = sum(10**k for k in range(0,N,d))
+            for i in range(lo//BB, hi//BB+1):
+                if i < B//10:
+                    continue
+                if i >= B:
+                    break
+                id = i*factor
+                #print(lo,hi,factor,i,id)
+                if lo <= id <= hi:
+                    #assert(str(i)*(N//d) == str(id)), (i,id)
+                    #print(lo, hi, i,B,id)
+                    yield id
+
 #solve("sample")
 solve("input")