The Artists | Think Like A Coder, Ep 5

翻译人员: Carol Wang 校对人员: Jiasi Hao

[ 像程序员一样思考 ]

[ 地点：198 树林 ]

[ 第五集 艺术家们 ]

Dawn and the train are both breaking when Ethic and Hedge arrive in the woods.

破晓时分，火车停下， 艾斯克和海吉抵达了树林。

The adventurers have recovered the first artifact—

这两位冒险者 已找到第一件神器 ——

the Node of Power—

能量晶石，

and have come to the 198forest in search of the second.

现抵达 198 森林， 来找寻第二件神器，

Here they’re welcomed by the director of the colony, Octavia.

殖民首领奥克塔维亚 欢迎他们的到来。

She established this treehouse sanctuary

机器人把人们从工作中解放后，

after the robots freed everyone from having to work.

她建立了这个树屋保护区。

It was meant to be a haven where people could follow their passions,

这本应是人们追随自己激情、

take up crafts, and find fulfillment.

从事手工业，获得成就感的港湾，

Which they did… at first.

一开始，人们也确实是这么做的，

Some years ago everyone forgot the point.

但几年前，大家都忘记了初衷，

They abandoned arts and crafts

他们放弃了艺术和手工，

and instead just painted and exhibited pictures of themselves

只是不停地画自己， 并展示自己的照片，

over, and over, and over.

日复一日，年复一年。

The location of the second artifact is no secret;

第二件神器的位置众所周知，

it’s in a tower, guarded by a garrison of bots,

位于一个万丈深谷的塔里，

由机器人看守， 有众多不为人知的陷阱。

a bottomless ravine, and who knows what other traps.

As soon as the tower went up with the node inside,

藏有能量晶石的塔高耸入云，

human communication across the land went dark.

整个地球的人类交流 在该塔建成后从此中断。

Octavia’s been after it for years,

奥克塔维亚关注它好几年了，

but try as she might, the defenses thwart her.

但无论她怎么尝试， 都无法突破其防御系统。

In order to even get to the tower, the team will need a distraction.

艾斯克团队为到达塔下， 需要分散守卫的注意力。

Octavia has an idea:

奥克塔维亚有个主意：

stir up the people through some well-intentioned vandalism.

通过一些善意的破坏公物行为， 来煽动人们（从而转移守卫视线）。

The residents’ paintings are all squares that come in different sizes,

居民画像是大小不一的正方形，

all an odd number of pixels across.

每个方向的像素数都是奇数。

Helper-bots pick up the finished portraits

机器人助手收集画完的肖像，

and hang them in public places for everyone to admire.

并挂在公共场所供大家欣赏。

There’s a slim margin of time when Hedge can access the paintings.

海吉只有极短的时间窗口 能接触到这些画，

如果它在每幅画上涂个 X，

If he were to deface each one with an X,

the people would blame the helper-bots,

人们就会责怪机器人助手，

creating just the distraction the team needs.

从而实现他们 分散机器人注意力的目的，

If only it were so easy.

要是实现起来 也如此容易就好了，

Hedge can’t just paint an X—

海吉不是如此简单就能画上 X，

his painting processor requires very specific instructions.

它的绘画处理器 需要非常具体的指令。

Treating the paintings as square grids,

它把这些画当作正方形网格，

he can fill in one pixel, or little square, at a time.

一次只能填一个像素， 即只能填一个小正方形。

He can move forwards and make 90 degree turns over the canvas,

它在画布上可以向前移动， 也能进行 90 度旋转，

but can’t move diagonally.

但不能斜着移动。

How does Ethic program Hedge to paint an X over each portrait?

艾斯克如何编程， 才能让海吉在自画像上涂上 X 呢?

Pause now to figure it out for yourself.

[ 可暂停播放自行解题 ]

[ 涂画规则 4 ]

[ 涂画规则 3 ]

[ 涂画规则 2 ]

[ 涂画规则 1 ]

[ 思路 5 ]

[ 思路 4 ]

[ 思路 3 ]

[ 思路 2 ]

Here’s a hint.

思路如下：

Try drawing a square grid like this,

先画一个正方形网格，如图，

and simulating Hedge’s path over it.

然后模拟海吉的涂画路径。

What patterns can you find to guide him?

如何指导海吉完成任务呢？

[ 按暂停自己解题 ]

Pause now to figure it out for yourself.

[ 答案公布 3 ]

[ 答案公布 2 ]

[ 答案公布 1 ]

The challenge here is to craft a set of instructions

这里的挑战是如何设计指令组，

that will work for any square grid.

以适用任何大小的正方形网格。

Fortunately, one of the strengths of programming

幸运的是，编程的优点之一 就是其灵活性，

is the flexibility to solve not just one problem,

它并非只能解决一个问题，

but a whole class of them all at once.

而是一次性解决一类问题。

It often helps to start with one case, and work towards the general.

先从一个案例开始着手， 总有助于找到整体方案。

Let’s say we had this square.

我们假设正方形如图所示，

Hedge can measure the length of its sides and store that number as a variable.

海吉可测量其边长， 并保存为变量值。

Now, what we need is a plan for how Hedge will paint an X,

现在，我们需要一个计划， 让海吉把像素逐个画上 X 。

pixel by pixel.

There’s more than one right answer for how to do this;

实现方法不止一个，

我们先来看两个方法。

let’s look at two.

First, what if Hedge went row by row, like a typewriter?

第一种，打字机模式， 让海吉一行一行地画。

If it’s a 9 pixel by 9 pixel painting,

如果画像是 9 X 9 像素，

in the first row he’d paint, skip 7, and then paint again.

它先画第一行第一格， 跳过七格，然后画一格，

In the second row he’d skip the first, paint, skip 5, and paint.

第二行，他跳过第一格再画， 跳过五格再画，

And so on.

继续画下一行。

The pattern here is that for each row the pixels skipped at the beginning

规则是，每行开始跳过的像素 +1，

go up by one,

and the pixels skipped in the middle go down by 2.

中间跳过的像素 -2，

海吉画到中心点时， 情况变得更加复杂。

Things get more complicated when Hedge reaches the center.

Here there’s a row with just one pixel painted.

这一行只画一个像素。

Then the whole thing reverses—

然后，画的顺序就全反了 ——

the number of pixels skipped goes down by one each time on the left,

左边跳过的像素数每行 -1，

and up by two each time in the middle.

每行中间跳过的像素数 +2。

Instructing Hedge to do this with a series of loops will work

海吉执行这组循环指令是可行的，

and is a perfectly fine solution.

且是完美解决方案。

The main drawback is that this requires quite a bit of logic—

主要缺点是其中涉及的逻辑很多——

knowing what to do in the middle, when to reverse the process,

每行中间做什么、何时反向操作，

and exactly how to reverse it.

以及如何精确反向操作。

So how might we approach this

那么，我们如何操作，

so that the logic remains consistent from start to finish?

才能使逻辑始终一致呢?

The key insight is to look at a grid as a series of concentric squares.

关键是把网格 看作是一系列的同心正方形。

每个正方形遵循相同模式——

Each square follows the same pattern—

painted pixels in the corners, and unaltered pixels in between.

只画四个角的像素， 其余像素不变。

So if we can figure out a way to paint one nested square,

因此，如果我们能找到 绘制一个嵌套正方形的方法，

transition to the next, and repeat, we can paint them all.

即可应用到下一个，不断重复， 就能把它们全部绘制出来。

Painting the outermost one is easy.

最外层正方形最容易绘制。

Start in a corner and paint that pixel.

从一角开始，先画该角的像素。

If we call the length of the painting n,

假设画的长度为 n 像素，

就向前移动 n - 1 格，

fly forward n minus 1 spaces.

Paint another pixel, and turn right.

再画一个像素，然后右转。

Now do the whole thing again… and again.

接着再做一次循环操作 ， 接着再做一次，

Now move forward one less space, turn right, fly forward once,

现在向前少移动一格， 右转，再向前移动一格，

海吉正好位于 下个同心正方形一角，

and Hedge will be in the next concentric square

and ready to repeat the whole process.

即可重复下一个循环过程。

Each square is n minus 2 pixels smaller than the last in length and width,

每个正方形的长宽 都比上一个少 n - 2 像素，

and we can follow this spiral pattern all the way to the center

继续该螺旋模式，

通过变量和循环控制海吉的步伐， 最终一直画到中心点。

with a loop and a variable that tracks how far Hedge should fly.

Is one of these methods better than the other?

两种方式哪种更优呢?

这取决于你的侧重点。

It really depends on what you value.

The strength of the spiral is the simplicity of finding a pattern

螺旋循环的优点在于， 它简单地找到一个模式，

and reusing the same logic from start to finish.

并从头到尾循序相同逻辑。

The advantage of the typewriter approach

打字机方法的优点在于，

is that it’s a more generalized solution,

它是一个更通用的解决方案，

meaning it can be adapted much more simply to fill in any pattern.

即它容易适应任何模式。

对艾斯克来说，哪种都能达成目的。

For Ethic’s sake, either will do just fine.

So here’s what happens.

所以结果是这样的，

海吉很快弄脏了所有的肖像，

Hedge rapidly defaces all of the portraits.

And within moments

不一会儿，

cries of anguish break out all over the forest.

痛苦的哭声响彻整个森林。

守卫塔的守卫们 离开了他们的岗位，

The garrison guarding the tower abandon their posts

to calm the agitated people,

以安抚骚动的人们，

and Ethic, Hedge, and Octavia slip through—

艾斯克、海吉和奥克塔维亚 悄悄穿了过去 ——

and nearly slip into the depths of the gorge

差一点掉进幽幽深谷，

standing between them and the tower.

那位于他们和塔之间的万丈峡谷。