Question 148

There is a vertical stack of books marked 1, 2 and 3 on Table-A, with 1 at the bottom and 3 on top. These are to be placed vertically on Table-B with 1 at the bottom and 2 on the top, by making a series of moves from one table to the other. During a move, the topmost book, or the topmost two books, or all the three, can be moved from one of the tables to the other. If there are any books on the other table, the stack being transferred should be placed, on top of the existing books, without changing the order of books in the stack that is being moved in that move. If there are no books on the other table, the stack is simply placed on the other table without disturbing the order of books in it. What is the minimum number of moves in which the above task can be accomplished?

Solution

For min steps 1st move would be to place book 3 from A to B

2nd move would be to place book 2 from A to B,

3rd move would be to place book 2 and 3 from B to A.

Last move would be to place books 2,3,1 from table A to Table B.

So 4 moves are atleast needed.

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