Swift Fun case of the Nottingham Tower

"Problem description"
There is a Vatican tower called Hanoi, there are three pillars A, B and C on the Hanoi Tower, there are several discs on column A, all discs of different sizes, and small in the large under, as shown:

Move all the discs on column A with pillar B to column C, move the process to move only one disc at a time, and still be small after the large in the lower, as shown:

The moving process of all discs.

"Design Ideas"

When column A has 1 discs, it is only necessary to move the disc from column A to column C.

When the column A has 2 discs, first move the disc above the column A from pillar A to column B, and then move the disc under Column A from column A to column C, and finally move the disk of column B from pillar B to column C.

When column A has 3 discs, the two discs above the column A are moved from pillar A to pillar B, and then the bottom disc of pillar A is moved from column A to column C, and finally the two discs of Pillar B are moved from pillar B to pillar C with column A.

In general, when column A has n disks, from top to bottom numbered 1, 2, 3, ...., N, first the column A above the number 1 to n-1 of the disk from pillar A through column C to the column B, and then the column a the bottom of the number of n is moved from column A to column C, and finally the column B of N- 1 discs are moved from pillar B to pillar C with column A.

The problem is to move the n discs of pillar A through column B to column C. Combined with the general steps above, it's easy to think of recursion. Assuming that the recursive function Playhanoitower (n, A, B, C) is used to move n discs from pillar A to column C, the function move (n, a, c) is used to move a disk numbered n from column A to column C, the general steps above can be expressed as:

1. When n = 1 o'clock, call Move (1, A, C) to move the disc from column A to column C.

2. When n > 1 o'clock,

1) Call Playhanoitower (N-1, a,c, b) and move the disk with column A above the number 1 to n-1 from pillar A to column B by Pillar C;

2) call Move (n, A, C) to move the disc numbered N on column A from column A to column C;

3) Call Playhanoitower (n-1, B, A, C) and move the n-1 disc of pillar B from pillar B to column C.

"Swift Programming Implementation"

var count = 1

Move the N-numbered disc from the post to the pillar to

func Move (n: Int, from: Character, to: Character) {

    Print("section\(Count) Step: Move\(N) Number disc,\( from)--->\( to)")

Count + = 1

}

Move n discs from pillars to pillars Dependon

func playhanoitower (n: Int, from: Character, Dependon: Character , to: Character ) {

//Only one disc with number 1

ifn = = 1 {

//The disc numbered 1 is moved from the pillar to the pillar to

Move(n: 1, From:from, to:to)

} else {

//Move the topmost n-1 disc from the pillar from the column to the Pillar Dependon

playhanoitower(N- 1, from:from,dependon:to, To:dependon)

//The disk numbered n is moved from the pillar to the pillar to

Move(n, From:from, to:to)

//The topmost n-1 disc is moved from pillar Dependon to pillar to

playhanoitower(N- 1, From:dependon,dependon:from, to:to)

}

}

Playhanoitower(n:5, from:Character("A"), Dependon:Character("B") to:Character("C"))

"Run Results"

1th step: Move the 1th-disc, A--->c

2nd Step: Move the 2nd-disc, A--->b

3rd Step: Move the 1th-disc, C--->b

4th Step: Move the 3rd-disc, A--->c

5th: Move disc 1th, B--->a

6th: Move disc 2nd, B--->c

7th step: Move the 1th-disc, A--->c

8th step: Move the 4th-disc, A--->b

9th step: Move the 1th-disc, C--->b

10th Step: Move the 2nd-disc, C--->a

11th: Move disc 1th, B--->a

12th Step: Move the 3rd-disc, C--->b

13th step: Move the 1th-disc, A--->c

14th Step: Move the 2nd-disc, A--->b

15th step: Move the 1th-disc, C--->b

16th Step: Move the 5th-disc, A--->c

17th: Move disc 1th, B--->a

18th: Move disc 2nd, B--->c

19th step: Move the 1th-disc, A--->c

20th: Move disc 3rd, B--->a

21st Step: Move the 1th-disc, C--->b

22nd Step: Move the 2nd-disc, C--->a

23rd: Move disc 1th, B--->a

24th: Move disc 4th, B--->c

25th Step: Move the 1th-disc, A--->c

26th Step: Move the 2nd-disc, A--->b

27th Step: Move the 1th-disc, C--->b

28th Step: Move the 3rd-disc, A--->c

29th: Move disc 1th, B--->a

30th: Move disc 2nd, B--->c

31st Step: Move the 1th-disc, A--->c

For more swift fun stories, see the 51CTO Academy Video: "The case of the Super Brother Video auditorium to conquer Swift (2nd season: Fun case)"

This article from "Super elder brother Video lecture" blog, declined reprint!

Swift Fun case of the Nottingham Tower