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• Upon emerging from stasis, Ethic is the unfortunate recipient of three surprises.

• The first: a prison cell.

• The second: complete amnesia.

• And the third: a mysterious stranger has gotten stuck

• squeezing through the bars on her window.

• His name is Hedge, and he has come to help Ethic save the world.

• But first they have to break out of jail.

• Hedge turns his hand into a lockpick and outlines the challenge ahead.

• Each lock in the prison works in the same unusual way.

• Inside the keyhole is a red dial that can be rotated to one of 100 positions

• numbered 1 through 100.

• The key for a given cell spins the dial to the right position,

• which, when stopped there, makes it turn green and unlocks the door.

• It would be out of the question to steal keys from a guard,

• but Hedge has a better idea.

• Hedge can carry out Ethic's commands.

• If Ethic tells him to walk 5 steps forward,

• turn right, then walk another 5 steps,

• that's exactly what he'll do.

• Hedge needs specific instructions though.

• If Ethic sayspick the lockortry every combination

• that would be too vague, butspin the dial 5 positions forwardwould work.

• Once out of the cell, they will only have a few moments to crack the lock

• for the outer prison door too before the guards catch them.

• So what instructions will allow Hedge to efficiently open any door?

• Pause now to figure it out for yourself.

• Before we explain the solution, here's a hint.

• A key programming concept that can help unlock the door is called a loop.

• This can be one or more instructions that Hedge will iterateor repeat

• a specified number of times,

• likejump up and down 100 times.”

• Or an instruction that Hedge will repeat until a condition is met,

• such askeep jumping up and down until it's 7 o'clock.”

• Pause now to figure it out for yourself.

• The first thing that's clear is that you need to find a way for Hedge

• to try every combination until one works.

• What takes a little more effort is how exactly you do so.

• One solution would be to instruct Hedge to try every combination in succession.

• Try 1 and check the light.

• If it turns green, open the door, and if not, try 2.

• If that doesn't work try 3. All the way up to 100.

• But it would be tedious to lay that out in its entirety.

• Why write more than 100 lines of code,

• when you can do the same thing with just 3?

• This is where a loop comes in.

• The lock has 100 positions,

• so Ethic could sayCheck the dial's color, then spin the dial forward once,

• for 100 repetitions.

• Remember where the dial turns green, then have Hedge set it back to that number.”

• A loop like this, where you specify the number of times it repeats,

• is called a “for" loop.

• But an even more efficient loop

• would have Hedge spin the dial one position at a time until it turns green

• and as soon as that happens, have him stop and open the door.

• That way if the door unlocks on 1,

• he doesn't need to cycle through all the rest of the numbers.

• This is anuntilloop,

• because it involves doing an action until a condition is met.

• A similar, alternate approach would be to turn the dial while it's still red,

• then stop.

• That's called a “whileloop.

• Hedge loops through the combinations, and the cell opens at 41.

• Ethic and Hedge wait until the perfect moment in the guards' rotation

• and make a break for it.

• Soon, Ethic faces a choice: hide inside a mysterious crystal,

• or try to crack the outer door and make a run for it.

• Ethic chooses to run.

• The second door takes Hedge longer, requiring him to spin all the way to 93.

• But he gets it open

• and takes the opportunity to explain why he's rescued Ethic.

• The world is in turmoil:

• robots have taken over, and only Ethic can set things right.

• In order to do so,

• they'll need to collect three powerful artifacts

• that are being used for nefarious purposes across the land.

• Only then can Ethic return to the world machinethat giant crystal

• to set things right.

• Ethic may have escaped the prison

• but what has she gotten herself into?

Upon emerging from stasis, Ethic is the unfortunate recipient of three surprises.

B1 中級 美國腔

越獄｜像編碼員一樣思考，第1集。 (The Prison Break | Think Like A Coder, Ep 1)

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ktyvr258 發佈於 2021 年 01 月 14 日