One Hundred Forty Five Doors
A prisoner was thrown into a
medieval dungeon with 145 doors. Nine, shown by black bars, are locked, but
each one will open if before you reach it you pass through exactly 8 open
doors. You don’t have to go through every open door but you do have to go
through every cell and all 9 locked doors. If you enter a cell or go through a
door a second time, the doors clang shut, trapping you.
The prisoner (in the lower
right corner cell) had a drawing of the dungeon. He thought a long time before
he set out. He went through all the locked doors and escaped through the last,
upper left corner one.
What was his route?
Puzzle provided by Kordemsky: The Moscow