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 INTRODUCTORY PROGRAMMING CMP-0005A Time allowed: 2 hours Answer BOTH questions from Section A and ONE question from Section B. All questions carry equal weight. Notes are not permitted in this examination. Do not turn over until you are told to do so by the Invigilator. CMP-0005A 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 eight syntax errors. Describe (24 marks) each of them using the line numbers to identify them. If you mention more than eight errors only the first eight will be considered for marking. 1 #include <iostream> 2 #include <vector> 3 #include <random> 4 using namespace std; 5 6 int radixsort(vector <unsigned> & vec) 7 8 unsigned * low = new unsigned[vec.size()]; 9 unsigned high = new unsigned[vec.size()]; 10 int max = 0; 11 for (int i = 0 ; i < vec.size ; i++) 12 if (vec[i] > max) max = vec[i]; 13 int pass = 0; 14 while (max <> 0) max =/ 2; 17 pass++; int divisor = 1; 20 for (int iter = 0, iter < pass ; iter++, divisor *= 2) int lowcount = 0, highcount = 0; 23 for (int j = 0 ; j < vec.size() ; j++) if ((vec[j] / divisor) % 2) 26 high[highcount++] = vec[j] 27 else 28 low[lowcount++] = vec[j]; int k = 0;

3 Page 3 31 for (int j = 0 ; j < lowcount ; j++, k++) 32 vec[k] = low[j]; 33 for (int j = 0 ; j < highcount ; j++, k++) 34 vec[k] = high[j]; int main() srand(123); 41 vector vec; 42 for (int i=0 ; i < ; i++) 43 vec.push_back(rand()); 44 radixsort(vec); 45 return 0; 46 TURN OVER

4 Page 4 (b) An inexperienced programmer has written the following program. Provide an improved version. (16 marks) #include <iostream> #include <random> using namespace std; int count1 = 0, count2 = 0, count3 = 0, count4 = 0, count5 = 0, count6 = 0, i = 0, k = 0; int main() srand(123); while (i < 10000) i++; k = rand() % 6 + 1; if (k == 1) count1 = count1 + 1; else if (k == 2) count2 = count2 + 1; else if (k == 3) count3 = count3 + 1; else if (k == 4) count4 = count4 + 1; else if (k == 5) count5 = count5 + 1; else if (k == 6) count6 = count6 + 1; cout << count1 << << count2 << << count3 << ; cout << count4 << << count5 << << count6 << endl; return 0; 2. You are given the following partially implemented program and asked to finish its implementation (without changing what has already been written). #include <iostream> #include <iomanip> using namespace std;

5 Page 5 struct Time int hour; int minute; int second; ; int main() while (true) cout << "enter a time in format HH:MM:SS > "; Time start = readtime(); cout << "enter a time in format HH:MM:SS > "; Time end = readtime(); if (smallertime(start, end)) cout << "The time difference is: "; // print time in format HH:MM:SS printtime(timediff(start, end)); return 0; (a) Write a function int timetosecond(time time) that returns the number of seconds corresponding to time. (b) Write a function Time secondtotime(int second) that returns a time that corresponds to a number of seconds. (c) Write a function Time timediff(time start, Time end) that returns the time difference between end and start. This function may use functions of question 2a and 2b. (d) Write the function Time readtime(). The input format is specified by the first two output messages printed by the code provided. (e) Write the function void printtime(time t). Pay attention to the printing format indicated by the comment in the code provided. (f) Write the function bool smallertime(time t1, Time t2) that returns true if time t1 is before time t2 and false otherwise. (7 marks) (8 marks) (7 marks) (6 marks) (6 marks) (6 marks) TURN OVER

6 Page 6 SECTION B Answer ONE question from this Section. All questions carry equal weight. 3. The objective of this exercise is to write a program that simulates ten tosses of a fair coins (a coin is fair if it is equally likely to show head or tail when tossed) and counts the number of tails obtained. The simulation should run for 1,000,000 experiments and a graphical output of the distribution of the results should be produced. If 834 experiments resulted in no tails, 9561 experiments resulted in 1 tail,... the output would be as shown in Figure 1. 0: 834 1: **9561 2: ******* : ******************* : ********************************* : **************************************** : ********************************* : ******************* : ******* : ** : 843 Figure 1. Distribution of the number of tails obtained in ten tosses of a fair coin. (a) Write a function int experiment() that returns the number of tails obtained in ten tosses of a fair coin. (b) Write a function double starvalue(vector<int> const & count) that returns the amount represented by a star if one represents the largest element in count by forty stars in a histogram. (c) Write a function void display(vector<int> const & count) that outputs the results contained in count graphically as in Figure 1. The maximum value stored in count should be represented by forty stars. You may want to use the function of question 3b. (d) Write a main program that performs 1,000,000 experiments and displays the results obtained using the display function of question 3c.

7 Page 7 4. You are given the following types that have been defined to record information about items that are sold by a shop. struct StockItem string code; int quantity; double value; ; // unique code that identifies a product // number of product items in the shop // value of one item typedef vector<stockitem> Store; Note that a product sold by a shop may be out of stock; that is quantity may be equal to zero. You are asked to implement the functions bool issold(string acode, Store const & store, int & indexstore); bool addtostore(stockitem item, Store & store); bool changeq(string acode, unsigned aquantity, Store & store); double storevalue(store & store); with the following requirements: (a) issold should return true if the product with code acode is sold by the shop, and false otherwise. In the former case the function should also set indexstore to the index of the product in store. (b) addtostore should add a stock item to the store and return true. However, 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) changeq should adjust the quantity of an item in store. The method should return false if no item with code acode is sold by the shop, and true otherwise. (d) storevalue should return the total value held by the store. END OF PAPER