Ethan’s 2 solutions of expressing pieces on Chinese chess board

Ethan just wrote the embedded for loops to print out 90 points of an empty Chinese chess board.

for j in 0..<10 {
for i in 0..<9 {
desc = desc + " ."
}
desc = desc + "\n"
}

It looked like:

 . . . . . . . . .
. . . . . . . . .
. . . . . . . . .
. . . . . . . . .
. . . . . . . . .
. . . . . . . . .
. . . . . . . . .
. . . . . . . . .
. . . . . . . . .
. . . . . . . . .

Next, what could we use to represent pieces on it?

To kick off our discussion, I wrote the following for him.

 r: red
b: black

r: rook 车(城堡)
n: knight 马(骑士)
b: bishop 象(大主教)
w: warrior 士(勇士)rb
k: king 将(国王)
c: cannon 炮(加农炮)
p: pawn 卒(小兵)

Ethan came with an idea in no time: “I would use 2 letters for each piece.”

“Do you mean something like this?”, I tried to confirm that I did get it.

 rrrn. . . . . . .
. . . . . . . . .
. . . . . . . . .
. . . . . . . . .
. . . . . . . . .
. . . . . . . . .
. . . . . . . . .
. . . . . . . . .
. . . . . . . . .
brbn. . . . . . .

“Yes”, he said.

“OK, I’ll leave it to you then”, I passed the control of screen to him.

He carefully deployed all the pieces, with nice spaces added also.

 rr rn rb rw rk rw rb rn rr
. . . . . . . . .
. rc . . . . . rc .
rp . rp . rp . rp . rp
. . . . . . . . .
. . . . . . . . .
bp . bp . bp . bp . bp
. bc . . . . . bc .
. . . . . . . . .
br bn bb bw bk bw bb bn br

Class was over.

Here was the homework for him: “@Ethan HW: work out some different plans to use letters or numbers to show 32 pieces. You can talk with your friends or family. Try to find the best solution”.

A few minutes later, Ethan posted his 2nd option in WeChat.

I was happy with that. So I went on with: “@Ethan keep trying to see if you can find a solution with only a single letter, instead of two, for each piece. Post it here when you have one. So far both the solutions need 2 letters for each piece”.

Then a voice message came from the other end: “Sure, Uncle. I’ll think about the other solutions. But it’s late now and I would go to sleep”.

We met again in the next class. Ethan told me: “I failed to figure out any way with a single letter”. I said: “no worry. I actually like your 2nd solution, which uses digits. Let me make a copy of it”. So I went on and copied those text.

 r3 r4 r5 r6 r7 r6 r5 r4 r3
. . . . . . . . .
. r2 . . . . . r2 .
r1 . r1 . r1 . r1 . r1
. . . . . . . . .
. . . . . . . . .
b1 . b1 . b1 . b1 . b1
. b2 . . . . . b2 .
. . . . . . . . .
b3 b4 b5 b6 b7 b6 b5 b4 b3

Ethan was proud of his work and shouted: “you forget to copy the part above it.”

 1=p
2=c
3=r
4=n
5=b
6=w
7=k

Oops, I didn’t realize the weight of his hard work. Every char matters in kids’ heart.

OK, it was time to reward his hard work. So I provided the final hint: “Do you know in English there are lower case and upper case?”

A few seconds passed in silence.

Then Ethan spoke loudly: “I got it!” This is the final version:

 R N B W K W B N R
. . . . . . . . .
. C . . . . . C .
P . P . P . P . P
. . . . . . . . .
. . . . . . . . .
p . p . p . p . p
. c . . . . . c .
. . . . . . . . .
r n b w k w b n r

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