[racket] scheme programming

Hi, I am freshman on this group. I think many of you can help me on programming scheme :)) because I am beginner but I can understand when I see how coded a question. and this helps me be good at scheme.

> For example wanna make sth like that;

> 

> ( 
)

> 

> ( )

> Database:

> 

> (define flights

> ‘((f237 istanbul frankfurt 5)

> (f220 newyork frankfurt 10)

> (f225 newyork paris 15)

> (f110 berlin moscow 6)

> (f050 istanbul moscow 3)

> (f105 frankfurt istanbul 5)

> (f023 istanbul tehran 4)

> (f338 tehran paris 7)

> (f461 frankfurt paris 2)

> (f173 frankfurt newyork 10)

> (f290 paris newyork 15)

> (f190 moscow paris 5)

> (f320 paris tehran 7)

> (f240 newyork moscow 18)))

> 

> (define passengers

> ‘((jake istanbul frankfurt)

> (mike newyork istanbul)

> (pier istanbul berlin)

> (hans frankfurt moscow)

> (john newyork istanbul)))




> I want to implement the
function find-flight which takes source and 


> destination as input (2
parameters) and returns flight number as a

> list with one element or nothing if no such flight exists.

> 

> > (find-flight 'istanbul 'frankfurt)

> (list 'f237)

> > (find-flight 'tehran 'istanbul)

> empty

> 

> For example, I wanna implement the function shortest-travel which


> takes passenger as input and
returns a list of flight numbers which

> is the travel alternative with the smallest total flight

> time. Again, you do not need to consider travel alternatives with

> more than one transit

> 

> > (shortest-travel 'jake)

> (list ‘f237)

> > (shortest-travel 'john)

> (list ‘f220 ‘f105)

> > (shortes-travel 'pier)

> (list 'f220 'f461)

> 

> If you help me, you will make a great favour to me :))

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