Can you put the books in order?
Ten books, two stacks. Move a block from the top of one stack onto the other. Sort them in at most 19 moves.
The clock starts when you reveal the puzzle.TEN VOLUMES. TWO PLACES TO PUT THEM.
A little disorder.
A clever way through.
Move a block.
Keep its order.
THE FINISH1 at the bottom → 10 at the topAll ten books in either stack.
Stack A
Stack B
Select a book and everything above it, then place the block on the other stack.
Drag a top block across, or select its lowest book and tap “Place here”.AT YOUR OWN PACE
A brain snack, with room to think.
THE ANSWER OPENS ANOTHER DOOR
Now for the lovely part.
You have an answer. Explore how it works, then take the idea somewhere new.
See why it works ↓Keep your time
THE IDEA BEHIND YOUR ANSWER
Build from the bottom.
Protect what is in order.
Replay your own transfers. Then see a method that works even when the starting disorder changes.
Stack A
Stack B
A PLAN YOU CAN REUSE
Grow a sorted foundation.
Gather the books into stack A. Transfer the top block whose lowest book is 1 to stack B. Book 1 now has its permanent place at the bottom.
To place 2, send the books above 1 back to A, then transfer the block beginning with 2 onto 1. Repeat for 3, 4 and onwards. The sorted foundation stays intact.
Gathering and placing 1 need at most two moves. Placing each of 2 through 9 needs at most two more. Book 10 needs at most one final move.
2 + 8 × 2 + 1 = 19 moves
Nineteen is a guarantee, not a minimum. Some transfers can be skipped. This starting layout also has a ten-move solution—an optional challenge for another visit.
The idea to take away
Keep a useful part of the result fixed. Once the bottom is in order, solve the smaller problem above it.