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riddles >> medium >> Wild wild west
(Message started by: Moti on Nov 25th, 2002, 7:36am)

Title: Wild wild west
Post by Moti on Nov 25th, 2002, 7:36am
Three cowboys are fighting for their lives, however, they don't all have equal shooting skills.
The grey cowboy has never missed a shot and has a 100%
chance of hitting the target.
The black cowboy hits every 2/3 and the red cowboy
(that's you) only get 1/3.

since the skills are not equal the judge decides to let you go first, then the black and finally the grey.

who would you shoot?    (and why)    :)

Title: Re: Wild wild west
Post by towr on Nov 25th, 2002, 7:52am
the judge..
(there's a similar riddle about cyborgs around here somewhere)

Title: Re: Wild wild west
Post by wowbagger on Nov 26th, 2002, 7:29am
The riddle employing cyborgs is titled "three-way pistol duel" and can be found in the hard section: http://www.ocf.berkeley.edu/~wwu/riddles/hard.shtml#threeWayDuel.

The forum thread is at http://www.ocf.berkeley.edu/~wwu/cgi-bin/yabb/YaBB.cgi?board=riddles_hard;action=display;num=1027808060.

The shooting skill of the black cowboy is different from the not-so-perfect cyborg, however. And the wording of the riddle is subtly different.

Title: Re: Wild wild west
Post by Speaker on Nov 28th, 2002, 12:20am
You need to shoot at grey first. He's the most dangerous so should be eliminated as soon as possible. (This also provides the most beneficial reduction in the likelyhood of being hit when you are shot at).

Next, black will either shoot at you are grey. If you managed to hit grey, then black will shoot at you. Allowing you a 1 in 3 chance of surviving, better than a none in none chance against grey.

But, if you didn't manage to hit grey, then black should use the same logic and shoot for the most dangerous adversary. (Also, by not shooting at black, black may assume some sort of alliance exists between you and him, which he may be foolish enough to honor).

If both black and you miss grey, then grey is going to eliminate one of you from the game. In this case he should go for black the most dangerous adversary.

This leaves you with a final chance to hit grey.

Which, should you miss, leaves nothing save dukincover.

Title: Re: Wild wild west
Post by towr on Nov 28th, 2002, 4:05am
Assuming that when there are only two players left they will shoot at each other, and that when there are three they can shoot the judge (a deliberate miss) if they deem it necessary,
there are 27 possibilities to play (one of which won't ever end).
Here's the complete list with chances (generated with model):
0)  [000]  red:0.00  black:0.00  grey:0.00
1)  [001]  red:0.00  black:66.67  grey:33.33
2)  [002]  red:33.33  black:0.00  grey:66.67
3)  [010]  red:0.00  black:0.00  grey:100.00
4)  [011]  red:0.00  black:22.22  grey:77.78
5)  [012]  red:11.11  black:0.00  grey:88.89
6)  [020]  red:42.86  black:57.14  grey:0.00
7)  [021]  red:28.57  black:60.32  grey:11.11
8)  [022]  red:39.68  black:38.10  grey:22.22
9)  [100]  red:0.00  black:0.00  grey:100.00
10)  [101]  red:0.00  black:44.44  grey:55.56
11)  [102]  red:22.22  black:0.00  grey:77.78
12)  [110]  red:0.00  black:0.00  grey:100.00
13)  [111]  red:0.00  black:14.81  grey:85.19
14)  [112]  red:7.41  black:0.00  grey:92.59
15)  [120]  red:24.49  black:32.65  grey:42.86
16)  [121]  red:19.05  black:40.21  grey:40.74
17)  [122]  red:26.46  black:25.40  grey:48.15
18)  [200]  red:14.29  black:85.71  grey:0.00
19)  [201]  red:4.76  black:73.02  grey:22.22
20)  [202]  red:26.98  black:28.57  grey:44.44
21)  [210]  red:6.12  black:36.73  grey:57.14
22)  [211]  red:4.76  black:43.39  grey:51.85
23)  [212]  red:12.17  black:28.57  grey:59.26
24)  [220]  red:30.61  black:69.39  grey:0.00
25)  [221]  red:23.81  black:68.78  grey:7.41
26)  [222]  red:31.22  black:53.97  grey:14.81

[012] means red will miss (0) in this problem that could be shooting the judge (considering it's a "_who_ will you shoot first?" question), black will shoot his worst opponent (1) in this case that's red, grey will shoot his best opponent (2) in this case that's black.

You can reduce the list by first letting grey optimize his choice, giving:
2)  [002]  red:33.33  black:0.00  grey:66.67
3)  [010]  red:0.00  black:0.00  grey:100.00
8)  [022]  red:39.68  black:38.10  grey:22.22
9)  [100]  red:0.00  black:0.00  grey:100.00
12)  [110]  red:0.00  black:0.00  grey:100.00
17)  [122]  red:26.46  black:25.40  grey:48.15
20)  [202]  red:26.98  black:28.57  grey:44.44
23)  [212]  red:12.17  black:28.57  grey:59.26
26)  [222]  red:31.22  black:53.97  grey:14.81

then black optimizes his choices:
8)  [022]  red:39.68  black:38.10  grey:22.22
17)  [122]  red:26.46  black:25.40  grey:48.15
26)  [222]  red:31.22  black:53.97  grey:14.81

from which red chooses his best choice:
8)  [022]  red:39.68  black:38.10  grey:22.22

having the best chance to survive out of the three

If you can't make a deliberate miss then the best red can do is:
26)  [222]  red:31.22  black:53.97  grey:14.81



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