Module Contact: Dr Pierre Chardaire, CMP Copyright of the University of East Anglia Version 1

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1 UNIVERSITY OF EAST ANGLIA School of Computing Sciences Main Series UG Examination 2014/15 INTRODUCTORY PROGRAMMING CMP-0005B Time allowed: 2 hours. Answer BOTH questions from section A and ONE question from section B. Notes are not permitted in this examination. Do not turn over until you are told to do so by the Invigilator. CMP-0005B Module Contact: Dr Pierre Chardaire, CMP Copyright of the University of East Anglia Version 1

2 Page 2 SECTION A 1. (a) The following C++ function contains a number of syntax errors. [16 marks] Identify and describe each syntax error. Use line numbers to identify the errors. 1 / / p r e c o n d i t i o n array of non negative i n t e g e r s 2 void r a d i x s o r t ( i n t a [ ], size ) 4 max =a [ 0 ] 5 for ( i =1; i < size ; i ++) 6 i f ( a [ i ] >max) max = a [ i ] ; 7 i n t passes = 1+ static_cast <int > ( f l o o r ( log10 (max ) ) ) ; 8 i n t d i v i s o r = 1; 9 i n t bucket [ 1 0 ] [ 2 0 ], bucket_size [ 1 0 ] ; 10 for ( i n t i t e r =0, i t e r < passes ; i t e r ++) for ( i n t i =0; i <10; i ++) 1 bucketsize [ i ] = 0 ; 14 for ( i n t i = 0; i < size ; i ++) i n t j = ( a [ i ] / d i v i s o r ) mod 10 ; 17 bucket [ j ] [ bucket_size [ j ] = a [ i ] ; 18 bucket_size [ j ] + + ; i n t k = 0; 21 for ( i n t i =0; i <10; i ++) 22 2 for ( i n t j =0; j <bucket_size [ i ] ; j ++) 24 a [ k ++] = bucket [ i ] [ j ] ; d i v i s o r = 10; CMP-0005B Version 1

3 Page (b) What is the purpose of the following function? Trace its execution to [8 marks] justify your answer. void vaihtaa ( i n t &a, i n t &b ) b=a+b ; a=b a ; b=b a ; (c) What is the following function supposed to do? Clearly justify your [8 marks] answer. You may want to trace the code with some of the inputs ROTOR, ROVER, NOON and NOOK. bool p e i l i ( s t r i n g &s ) for ( i n t i =0; 2 i < s. length ( ) ; i ++) i f ( s [ i ]!= s [ s. l ength () 1 i ] ) return false ; return true ; (d) What does the following function do? Clearly justify your answer. [8 marks] double keskiarvo ( void ) double m= 0.0; i n t n=0, x =1; cout << " enter a l i s t of numbers f o llowed by a zero > " ; c i n >> x ; do n++; m += ( x m) / n ; / / same as m = ( ( n 1) m +x ) / n c i n >> x ; while ( x! = 0 ) ; return m; CMP-0005B Version 1 TURN OVER

4 Page 4 2. There is no requirement to test for input ranges or carry out other validation in the following parts of this question. Comments should only be included if they are required to add clarity to the code. (a) Write a C++ code fragment to ask a user to enter an integer number, and output all positive numbers less than or equal to this number. (b) Write a C++ code fragment to ask a driver to enter a distance [15 marks] travelled in miles (mi) and the time it took to travel in hours (h), and output their average speed V = distance/time. The user should then be given the opportunity to enter another distance and time. (c) Moving averages are used to smooth data to more easily [15 marks] understand trends in the data. Given a sequence of n numbers a 1,a 2,a,...,a n its moving average sequence of period is given by a 1 + a 2 + a, a 2 + a + a 4, a + a 4 + a 5,..., a n 2 + a n 1 + a n Write a C++ code fragment to allow a user to enter any number of positive integers. When a zero integer is entered the code should output the moving average sequence of period three of the input sequence of positive numbers if the user has input at least positive numbers, otherwise it should terminate without outputing anything. CMP-0005B Version 1

5 Page 5 SECTION B Answer ONE question from this section.. A prime (short for prime number) is an integer number greater than 1 that has no divisors except 1 and itself. The objective of this exercise is to calculate and output the first (smallest) n primes. (a) Write a function that takes as input an integer number x and a vector of primes, and returns true if x is divisible by one of the primes in the vector and false otherwise. (b) Using the fact that an integer number, p, is prime if and only if no prime smaller than p divides p, write a function that takes as input a vector that contains all primes up to the n th prime and returns the (n + 1) th prime. Your function should utilise the function in Question a. (c) Write a function that takes as input an integer n and returns a vector that contains the first n primes. Your function should utilise the function in Question b. (d) Write a main function that asks the user for a number n of primes and outputs the first n primes, obtained by utilising the function in Question c. CMP-0005B Version 1 TURN OVER

6 Page 6 4. You are given the interface of a class whose instances are used to record information about items that are sold by a shop. class StockItem private : unsigned code ; / / unique code t h a t i d e n t i f i e s a product unsigned q u a n t i t y ; / / number of items i n the shop f l o a t u n i t c o s t ; / / cost of one item / / etc. Note that an item sold by a shop may be out of stock; that is quantity may be equal to zero. You may assume that this class provides public accessor methods to get and set the values of the data members, and a public method getstockvalue that returns the cost quantity*unitcost of the items in the shop. A class Stock, which contains as private data member a vector store of StockItem sold by a shop, is to be implemented. You are asked to write the following methods for this class: (a) bool issold(unsigned acode) to check whether store contains an item with code acode. (b) bool addtostore(stockitem item) to add a stock item to the store. If the stock item has the same code as an item already sold by the shop no addition should occur and false should be returned. (c) bool changeq(unsigned acode, unsigned aquantity) to adjust the quantity of an item in store. The method should return false if no item with code acode is sold by the shop. (d) float stockvalue() to compute the overall cost of the items in the shop. END OF PAPER CMP-0005B Version 1