Figure 4: The start-setting (top), an intermediate setting (center) and the end-state (bottom) for the N=2 MToH puzzle. The number of moves to progress from the start-setting to the intermediate state described by the center figure is 2. The number of moves to progress from the center-described state to the end-state described by the bottom figure is again 2. Thus, the (minimum) number of moves required to solve the puzzle is S(2) = 4. Note that two different solution routes, both of length 4, exist (1,2,1,1 – shown, 1,1,2,1 – not shown).
Consulting Figure 4 we find for the N=2 case -
. (4)
The small disk made 3 (=31) moves and the large disk made 1 (=30) move. Thus far then, for the N=1 and N=2 cases, base 3 is elegantly spanned as
and ; N = 1,2. (5)
Exactly analogous to the base 2 span by the classical ToH (Equation 1 and Equation 2).
But let's see now the N=3 case.
To conveniently talk about the N=3 case, let's (arbitrarily and without loss of generality) define the posts (refer to Figure 5 below) as
Let's also memorize the disk numbering convention:
Step number
|
Disks
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From
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To
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# of moves
|
Comments
|
1
|
2,3
|
S (Red)
|
I (Blue)
|
4
|
Equation 4
|
2
|
1
|
S (Red)
|
D (Blue)
|
1
|
S now free
|
3
|
3
|
I (Blue)
|
D (Blue)
|
2
|
Through S, S now free
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4
|
2
|
I (Blue)
|
S (Red)
|
1
|
Post I now free
Fig. 5 - middle
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5
|
3
|
D (Blue)
|
I (Red)
|
1
|
S and I are both Red
I switched BlueRed
|
6
|
2
|
S (Red)
|
D (Blue)
|
1
|
|
7
|
3
|
I (Red)
|
D (Blue)
|
1
|
Puzzle solved
|
|
|
|
|
11
|
Total # of moves
|
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