What you did recursively is ... - Move (n - 1) from peg1 to peg3 - Move 1 from peg1 to peg3 - Move (n - 1) from peg1 to peg3 .. which is not what you want. Keep thinking, you will get it. Some things to consider: - Distribute the discs on two intermediates. - Keep track of the order in which discs are assembled on the intermediates. - Move 1 disc from peg1 to peg4. - Then, move the distributed discs back in the reverse order from how you put them there. By keeping track, I mean keep track of which peg is filled first. Hope this helps. On 19 February 2015 at 19:20, Roelof Wobben wrote:

Hello,

I try now to make the optional exercise hanoi with 4 pegs,

So I did on paper this :

start temp1 temp2 end

3 2 1

first move : start -> temp2

start temp1 temp2 end 2 3 1

second move : start -> temp1

start temp1 temp2 end 1 2 3

now I tried to make this piece in code

So I did :

hanoi4 1 start _ _ end = "move 1 disk from " ++ [start] ++ " to " ++ [end] ++ ".\n" hanoi4 n start temp1 temp2 end = hanoi4 (n-1) start end temp1 temp2 ++ hanoi4 1 start end temp1 temp2 ++ hanoi4 (n-1) start temp1 end temp2

because on the first step start must be start and end must be temp1 and on the second step start must be start and end must be temp2

but when I run in I see this output :

move 1 disk from a to b. move 1 disk from a to b. move 1 disk from a to b. move 1 disk from a to c. move 1 disk from a to d. move 1 disk from a to d. move 1 disk from a to d.

Can anyone explain or let me see where my thinking took the wrong turn ?

Roelof

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