# CSE 341 Homework#2 solution

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## Description

Part 1. In the graph below you see the possible flights between some of the cities in Turkey. Write the
predicate “route(X,Y) – a route between X and Y exists” that checks if there is a route between any
given two cities.
Your program should have all the facts and predicates/rules. See the following:
% knowledge base

flight(istanbul,antalya). % the fact that Istanbul and Antalya has a flight.

% rules

route(X,Y) :- flight(X,Y). % a predicate indicating there exist a route between
% X and Y if there is flight between X and Y.

A single query to complete your program should check if there is a direct route between two given
cities. Alternatively, it can list all the connected cities for a given city. See the following:
?- route(edirne,X).
X = erzincan ;
X = edremit ;
Part 2. Continuing with the previous problem, you are asked to write a program that checks if a route
exists between two cities and if so provides the shortest route.
In the first step, you are to expand the knowledge by adding distances for the flights. E.g.,
% knowledge base

flight(istanbul, antalya). % the fact that Istanbul and Antalya has a flight.
distance(istanbul, antalya, 481). % flight distance – calculated using
% https://www.distancecalculator.net
% complete all the flights and distances …

A single query to complete your program should check if there is a direct route between two given
cities and the shortest distance between them. See the following:
?- sroute(edremit,erzincan,X).
X = 1044 ;
Part 3. You are given the following database about classes, classrooms and student enrollment.
Classes Enrollment
Class Time Room Student Class
102 10 z23 a 102
108 12 z11 a 108
341 14 z06 b 102
455 16 207 c 108
452 17 207 d 341
e 455
Write the predicates “when(X,Y) – time of the course X is Y”, “where(X,Y) – place of the course X is Y”,
and “enroll(X,Y) – student X is enrolled in course Y”. For example:
% facts..
when(102,10).
3.1. Define/write a predicate “schedule(S,P,T)” associates a student to a place and time of class. See
the example query and its result.
?- schedule(a,P,T).
P = 102
T = 10 ;
P = 108
T = 12 ;
3.2. Define/write another predicate “usage(P,T)” that gives the usage times of a classroom. See the
example query and its result.
?- usage(207,T).
T = 455 ;
T = 456 ;
3.3. Define/write another predicate “conflict(X,Y)” that gives true if X and Y conflicts due to classroom
or time.
3.4. Define/write another predicate “meet(X,Y)” that gives true if student X and student Y are present
in the same classroom at the same time.
Part 4. Write the following predicates operating on lists.
4.1. Define a Prolog predicate “add(L,S)” that adds all the elements of L binding the results to S.
4.2. Define a Prolog predicate “unique(L1,L2)” that removes duplicates in L1 binding the results to L2.
4.3. Define a Prolog predicate “flatten(L1,L2)” that flattens the list of lists (your can assume that
elements of L1 are not nested lists) in L1 binding results to L2.