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help a tiny Scheme problem

 
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help a tiny Scheme problem
kidworld
post 4 Nov, 2005 - 07:22 PM
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This is first time I played with Scheme, I got a question to design a scheme code to find a given undirected graph is connected. like ((a cool.gif (c d) (b d) (a c)) is connected but ((a cool.gif (c d) (b d) (a e)) is not connected. I try to thinking the soluion like what I did in C++, but failed . so I have no idea how to do this.
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cyberscribe
post 5 Nov, 2005 - 10:51 AM
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humble.genius

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QUOTE(kidworld @ Nov 4 2005, 09:19 PM)
CODE

((a b) (c d) (b d) (a c))

is connected but
CODE

((a b) (c d) (b d) (a e))

is not connected
  • This is a list; not an array.
  • This is recursion; not iteration.
  • This is Scheme; not C++

    Here's how I'd approach it: in recursion you can't "store" values, but you can pass them along so they persist. So, I'd start out with a function that takes two arguments: your original list, and a blank list. The second argument will be the stuff from the original list that is unmatched. Then you recurse through each pair, trying to match stuff in the pair against stuff left to be matched (i.e. first element to last element and last element to first element). When the first argument is empty, you check the second argument. If it's also emtpy, everything has been matched for continuity. Otherwise, if your matching algorithm is tight and there's stuff left to be matched, the graph is not continuous. Make sense?
Good luck! This one's tricky. smile.gif
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