Can you solve Dongle's Difficult Dilemma? - Dennis E. Shasha

2,261,685 views ・ 2021-04-26

TED-Ed


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翻译人员: Ruishi (Jerry) Zhang 校对人员: Helen Chang
00:06
According to legend, when this planet was young and molten,
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传说中,当这个星球 还年轻并炽热的时候
00:10
three galactic terraformers shaped it into a paradise.
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三个来自星系之外的异种 把这里变成了人间福地
00:15
When their work was done, they sought out new worlds,
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他们改造完星球后 开始了寻找新的星球的旅程
00:18
but left the source of their power behind:
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但是他们把他们的力量源泉 留在了星球里
00:21
three powerful golden hexagons,
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三个有着强大力量的黄金六角宝石
00:25
hidden within dungeons full of traps and monsters.
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这三个宝石被放在 充满陷阱和怪物的地下城里
00:28
If one person were to bring all three hexagons together,
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如果有人集齐了这三个宝石
00:32
they could reinvent the world however they saw fit.
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他就可以依意愿来重新改造这个世界
00:36
That was thousands of years ago.
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这件事发生在上千年前
00:39
Today, you’ve learned of Gordon, an evil wizard dead set on collecting the hexagons
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今天,你得知一个叫戈登的邪恶巫师 要集齐这三个宝石
00:45
and enslaving the world to his will.
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并奴役这个世界
00:48
So you set off on a quest to get them first,
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所以你决定抢在戈登之前 拿到这三个宝石
00:52
adventuring through fire, ice, and sand.
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你经过了火焰、寒冰,和狂沙的试炼
00:56
Yet each time, you find that someone else got there first.
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但是每次都有另一个人 在你之前拿到宝石
01:00
Not Gordon, but a merchant named Dongle.
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这个人不是戈登 他是一个叫当构的商人
01:04
At the end of the third dungeon. you find a note inviting you to Dongle’s castle.
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在第三个地下城里 你找到了来自当构城堡的邀请函
01:09
You show up with a wallet bursting with the 99 gems
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你带着在冒险时得到的99个宝石
01:13
you’ve collected in your travels,
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到达了当构的城堡
01:14
arriving just moments before Gordon, who also has 99 gems.
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戈登在你之后也到了 而且他也有99个宝石
01:20
Dongle has not only collected the golden hexagons,
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当构不止拿到了仅有的三个六边金宝石
01:24
but he’s used them to create 5 silver hexagons,
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他还用金宝石创造了五个六边银宝石
01:28
just as powerful as their golden counterparts.
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并且银宝石和金宝石有着相同的力量
01:31
Why did Dongle do all this?
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为什么当构要这么做呢?
01:33
Because there’s one thing he loves above all else: auctions.
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因为当构最喜欢拍卖
01:38
You and the evil wizard will compete to win the hexagons,
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你和邪恶的巫师要去竞拍这些六边宝石
01:43
starting with the three golden ones,
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从三个金宝石开始
01:45
making one bid for each item as it comes up.
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一个物品能出价一次
01:49
The winners of ties will alternate, starting with you.
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如果出价相同,胜者会轮换
从你开始
01:53
Whoever first collects a trio of either golden or silver hexagons
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第一个拿到三个相同颜色宝石的人 (不论金色还是银色)
01:58
can use their power to recreate the world.
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可以用它们的力量重塑这个世界
02:01
You’ve already bid 24 gems on the first,
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当你第一轮已经出了24个宝石的时候
02:05
when you realize that your rival has a dastardly advantage:
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你发现你的对手用了卑鄙的手段
02:09
a mirror that lets him see what you’re bidding.
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一个可以让他看到你出价的镜子
02:13
He bids zero, and you win the first hexagon outright.
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他的出价是0个宝石 你赢得了你一个宝石
02:17
What’s your strategy to win a matching trio of hexagons before your rival?
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你要怎么在戈登之前 集齐三个六边宝石呢?
02:22
Pause here to figure it out for yourself.
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如果想自己先算出来,在这里暂停
02:24
Answer in 3
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02:25
Answer in 2
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02:27
Answer in 1
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02:31
Dongle’s dangled a difficult dilemma.
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当构出了一个让人进退两难的难题
02:33
Do you spend big to try to win the golden hexagons outright?
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你要花大钱试图直接赢得 全部的金六边宝石吗?
02:37
Save as much as possible for silver? Or something in-between?
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还是攒钱去买银六边宝石? 或者在这两者之间?
02:42
Gordon can use his magic mirror and 99 gems
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戈登可以用他的神奇镜子和99个宝石
02:45
to make sure that no matter what you bid on the second gold,
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去确保不论你对第二个 金六边宝石的出价是多少
02:49
he can bid one more and block you.
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他都能比你多出一个宝石,胜过你
02:51
So the real question is— how can you force Gordon to spend enough on the golds
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那么问题来了——如何让戈登 在金六边宝石上花上够多的钱
02:57
to guarantee that you’ll win on the silvers?
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从而确保你能赢下银色的六边宝石呢?
03:01
Here’s a hint.
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给你点提示
03:02
Let’s say at the start of the silver auctions
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如果在开始竞拍银六边宝石的时候
03:05
you had a one gem advantage, such as 9 to 8.
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你比戈登多一个宝石 比如你有九个,他有八个
03:09
You need to win three auctions,
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你需要赢下三次竞拍
03:12
so could you divide your gems into three groups of three and win?
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那么你能把你的宝石 分成三组并取得胜利吗?
03:17
For simplicity, let’s assume a set of rules that’s worse for you,
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为了让情况变得更简单 我们假设有一个对你很不利的规则
03:21
where Gordon wins every tie.
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那就是每次出价一样都算是戈登获胜
03:24
If you bid 3 each time, the best he could do
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如果你每次出价三个宝石 戈登最多能赢下两个宝石
03:27
is win two silver hexagons, and have two gems left—
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并且只剩两个宝石
03:31
which you’ll beat with three bids of 3.
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那你就可以用你的三个宝石打败他
03:34
Any one-gem advantage where your starting total is divisible by three
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一样的逻辑 只要你的宝石数可以除以三
03:39
will lead to victory by the same logic.
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你就肯定能赢得最终的胜利
03:43
So knowing that, how can you force Gordon's hand in the gold auctions
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知道了这个后,如何让戈登 把更多钱花在金六边宝石上
03:47
so you go into silver with an advantage?
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以让你在银六边宝石的竞拍上 赢得优势呢?
03:50
Let’s first imagine that Gordon lets you win the second gold auction
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试想戈登出了和你一样数量的宝石
03:54
by betting some amount X with a tie.
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让你赢了第二个金宝石
03:58
You could then bid everything you have left on the third gold hexagon,
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接着不管你在第三个金宝石上出价多少
04:02
and he'd have to match you to block.
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他必须比你出的多 从而阻止你获得三个金宝石
04:05
So if you could bid 51 on the third gold,
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所以如果你在第三个金宝石上 出价51个宝石
04:08
you'd go into silver with a 51 to 48 advantage, which you know you can win.
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你将会以51比48的优势 参加银宝石竞拍,并且可以赢
04:15
Solving for X reveals that in order to have 51 on round three,
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经过计算,如果你想在 第三个金宝石竞拍时有51个宝石
04:20
you should bid at most 24 on round two.
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你第二轮最多出24个宝石
04:24
But what about the other possibility,
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但是如果戈登在第二轮
04:27
where Gordon wins the second gold against your bid of 24—
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出价超过24个宝石
04:31
would this strategy still work?
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这个计策还有用吗?
04:34
The least he could bid to win the second gold is 25,
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如果戈登想赢第二轮 他最少出25个宝石
04:38
making the total 75 to Gordon’s 74.
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这样的话你就有75个宝石 戈登有74个
04:42
No one would then bid on round three,
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紧接着没有人赢得第三轮
04:45
since you’ve each blocked the other from getting three golds.
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因为你和戈登互相牵制对方
04:49
After that, you could bid 25 every time to win three silvers.
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然后,你就可以每轮出价25 并赢下三个银宝石
04:55
The bidding war was close,
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竞拍结束了
04:56
but your ingenuity kept you one link ahead in the chain of inference,
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但是你的聪明才智使你比戈登更快一步
05:01
and the silver tri-source is yours.
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你得到了三个银六边宝石
05:04
Now... what will you do with it?
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那么现在,你要用它们做什么呢?
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