Foundation Exam - CS I Section

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Rumson Fair Haven Reg H *

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C101

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Computer Science

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Nov 24, 2024

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October 16 th Foundation Exam CS I Questions (1, 15%) The following (INCORRECT) algorithm is intended to be the iterative bubble sort algorithm. Assume that swap is a global procedure that exchanges the contents of its two parameters. algorithm Bsort(n) procedure B(k) 1) set j <- 1 2) while j < k do 3) if a[j] > a[j+1] then 4) swap(a[j], a[j+1]) 5) set j ß j + 1 endprocedure begin 6) for i = 1 to n-1 do 7) B(n-i); endalgorithm It SHOULD take this first list… 8 3 10 7 5 4 …and produce this list. 3 4 5 7 8 10 1a) But, it doesn't. What does it produce? 1b) There is one error in the algorithm. In which line does it occur? __________ 1c ) Write the correct pseudo-code for the line identified in 1b).
(2, 20%) The following are Postfix strings. All values are single decimal digits and the operations are binary add "+", binary subtract "-",and binary multiplication "*". Indicate which are invalid, if any. For those that are valid, compute the result. a) 9 4 + 2 3 * - 6 3 - 5 * + 7 - ___________________________ b) 8 3 2 4 * + - 7 8 2 3 * - + ________________________ c) 3 2 + 4 2 * 7 5 - 2 3 * + - + ________________________ d) Given the following Postfix expression, show in the boxes below what the stack would contain immediately before the - operation is processed. Do not find the final result. Assume that the stack is initially empty. 2 6 + 5 3 2 * - 5 * + (top of stack)
(3, 15%) The following insertion algorithm, Insert , must be invoked from the algorithm you are to write below. Assume that the variables j and x are local to the procedure and that k is an integer parameter. Procedure Insert(k) set j <- k set x <- a[j] while (j > 1) and (x < a[j-1]) do set a[j] <- a[j-1] set j <- j-1 set a[j] <- x end Write a recursive "InsertionSort" algorithm using Insert . You may assume a globally defined array a[1..n] of integer values that is already initialized. (4, 20%) Find the closed form or exact value for each of the following: ( n is an arbitrary positive integer): 4a) å (3i+2) = ( i ranges from 0 to n .) _______________________ 4b) å (2i-3) = ( i ranges from 50 to 200 .) ____________________
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4c) S = 5 + 6 + 7 + 8 + … + (n-2) + (n-1) = _____________________ 4d) t(n) = t(n-1) + 2, where t(0) = 1 ________________________ (5, 15%) Answer each of the following "timing" questions concerning an algorithm of a particular order and an instance of a particular size. a) For an O(n) algorithm, an instance with n = 50 takes 4 seconds. How long will it take with n = 250? ____________________ b) For an O(n 3 ) algorithm, an instance with n = 30 takes 20 seconds. How long will it take when n = 60? ____________________ c) For an O(2 n ) algorithm, an instance with n = 2 takes 12 seconds.
How long will it take when n = 3? ____________________ (6, 5%) Given the following procedure, fill in the blanks below to show the order in which the values of x will be output if the procedure is called with Print_it(5) . procedure Print_it(x) if (x = 1) then print(x) else Print_it(x-1) print(x) endif endprocedure Show, in order, the output from executing the procedure: ___________ ___________ ___________ ___________ ___________ (7, 10%) P is the class of problems known to be solvable in polynomial time, NP is the class that is verifiable in polynomial time (i.e., given the correct solution to an instance, we can verify its validity in polynomial time), and EXP are problems we know require exponential time to solve and to verify. Which is the most appropriate set for each of the following? Evaluate a postfix expression _________________ Finding the most distant pair in a list of n items _________________ Reverse a character string of n characters _________________ Find a cycle containing every node in a graph _________________ Finding the closest pair in a list of n items _________________ Search a list of n items for a given value _________________
Fitting a set of final exams into the shortest number of days_________________ Sort a list of n values _________________ Towers of Hanoi _________________ Find a subset of numbers which sum exactly to X _________________ Solutions to the CSI questions.
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