University of Calgary Department of Electrical and Computer Engineering ENCM 339: Programming Fundamentals, Section 01 Instructor: Steve Norman

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1 page 1 of 9 University of Calgary Department of Electrical and Computer Engineering ENCM 339: Programming Fundamentals, Section 01 Instructor: Steve Norman Fall 2017 FINAL EXAMINATION Location: ENG 60 Monday, December 11 Noon to 3:00 PM NAME (printed): Please don t write anything within this box. 1 / 10 2 / 12 U of C ID NUMBER: 3 / 9 4 / 12 5 / 5 SIGNATURE: 6 / 9 7 / 10 8 / 9 TOTAL / 76 Version information This docuemnt is very slightly different from the one that was printed and given to students. A typographical error has been corrected on page 5, and some text has been edited on page 7 to clarify the specifications of the functions students were asked to write. Instructions Please note that the official University of Calgary examination regulations are printed on page 1 of the Examination Regulations and Reference Material booklet that accompanies this examination paper. All of those regulations are in effect for this examination, except that you must write your answers on the question paper, not in the examination booklet. Calculators may not be used while writing this examination. The examination is closed-book. You may not refer to books or notes during the examination, with one exception: you may refer to the Examination Regulations and Reference Material booklet that accompanies this examination paper. You are not required to add comments to C or Python code you write, but you are strongly encouraged to do so, because writing good comments will improve the probability that your code is correct and will help you to check your code after it is finished. Some problems are relatively easy and some are relatively difficult. Go after the easy marks first. Write all answers on the question paper and hand in the question paper when you are done. Please do not hand in the Examination Regulations and Reference Material booklet. Please print or write your answers legibly. What cannot be read cannot be marked. If you write anything you do not want marked, put a large X through it and write rough work beside it. You may use the backs of pages for rough work.

2 ENCM 339 Fall 2017 Section 01 Final Examination page 2 of 9 PROBLEM 1 (total of 10 marks) Part a (5 marks). Make a memory diagram for the second time the program gets to point one. int add(const int *a, int m) { int s = a[0], i; // point one for (i = 2; i < m; i += 2) s += a[i]; return s; void foo(const int *b, int n, int *p, int *q) { *p = add(b, n); *q = add(b + 1, n - 1); int x[ ] = { 2, 3, 5, 7, 11, 13, 17 ; int j, k; foo(x, 7, &j, &k); Part b (5 marks). Here are some facts relevant to this part of the problem: isspace returns a nonzero value if its argument is a whitespace character (such as space or tab), and zero otherwise. isdigit returns a nonzero value if its argument is one of 0, 1, 2,..., 9, and zero otherwise. ASCII codes for digits are 48, 49, 50,..., 57. Make a memory diagram for the second time the program gets to point one. #include <ctype.h> int getint(const char *s, const char **n) { int r = 0; while (isspace(*s)) s++; while (isdigit(*s)) { r = 10 * r + (*s - 48); s++; // point one *n = s; return r; char foo[ ] = " "; int i1, i2; const char *p; i1 = getint(foo, &p); i2 = getint(p, &p); // point two Hint: At point two the values of i1 and i2 will be 23 and 456.

3 ENCM 339 Fall 2017 Section 01 Final Examination page 3 of 9 PROBLEM 2 (total of 12 marks) Part a (6 marks). Write a complete C function definition to match the given function interface. void remove(char *dest, const char *s1, const char *s2); // REQUIRES: s1 and s2 point to the starts of strings. dest points // to the start of an array of length at least strlen(s1) + 1. // PROMISES: A string is built in the dest array by copying characters // from the s1 string that are NOT in the s2 string. // EXAMPLE: remove(d, "programming", "aeiou") would put "prgrmmng" in // the array found with d. Part b (6 marks). In a two-dimensional coordinate system, the distance from a point (x, y) to the origin is x 2 + y 2. Write a complete C function definition to match the given function interface. (Hint: You will need to do some multiplying and adding, but won t need to take square roots.) struct point { double x, y; ; typedef struct point point_t; int i_of_max_dist(const point_t *a, int n); // REQUIRES: n >= 1, elements a[0]... a[n-1] exist. // PROMISES: Return value is the index of the element that has the // maximum distance from the origin. In the case of a tie, the // the smallest index of a maximum is chosen.

4 ENCM 339 Fall 2017 Section 01 Final Examination page 4 of 9 PROBLEM 3 (total of 9 marks). Miscellaneous short-answer questions about C. Part a (3 marks). Write the program output in the space below the program listing. #include <stdio.h> #define DIV(a, b) a / b #define SUB(c, d) c - d printf("div(20.0, DIV(4.0, 2.0)) is %f\n", DIV(20.0, DIV(4.0, 2.0))); printf("div(10, SUB(8, 3)) is %d\n", DIV(10, SUB(8, 3))); Part b (3 marks). Assume that the call to fopen is successful, that the contents of text file stuff.txt are as shown, and that the program is running on a platform where EOF is 1. #include <stdio.h> FILE *fp = fopen("stuff.txt", "r"); int code, last = -1, count = 0; while (1) { code = fscanf(fp, "%d", &last); if (code!= 1) break; count++; printf("code: %d; last: %d; count: %d\n", code, last, count); stuff.txt xyz What is the program output? Part c (3 marks). Write the program output in the space beside the program listing. Hint: 779 = #include <stdio.h> void do_something(int n) { static char hd[] = " abcdef"; char c; printf("got %d\n", n); if (n <= 15) c = hd[n]; else { do_something(n / 16); c = hd[n % 16]; fputc(c, stdout); do_something(779); printf("\nbye!\n");

5 ENCM 339 Fall 2017 Section 01 Final Examination page 5 of 9 PROBLEM 4 (total of 12 marks). The following program shows one way to program with matrices in C using a struct type and dynamically allocated arrays. If the malloc calls in init_mat succeed, the state of the program at point one will be what is shown in the diagram. #include <stdlib.h> #include <stdio.h> struct matrix { int nrow; int ncol; double **e; ; typedef struct matrix matrix_t; void init_mat(matrix_t *m, int nr, int nc) { m->e = malloc(nr * sizeof(double*)); double *block2 = malloc(nr * nc * sizeof(double)); int i; for (i = 0; i < nr; i++) m->e[i] = block2 + i * nc; m->nrow = nr; m->ncol = nc; double v[3]; matrix_t a; int s; init_mat(&a, 2, 3); for (int r = 0; r < 2; r++) for (int c = 0; c < 3; c++) a.e[r][c] = r * (c + 1); AR main point one a v[0] v[2] s nrow ncol e???????? 2 3 no parameters stack heap // point one get_col_sums(&a, v); s = save_to_file(&a, "my_mat.dat"); if (s!= 0) fprintf(stderr, "error (code %d) saving matrix to file!\n", s); Part a (6 marks). The function get_col_sums is supposed to compute the sums of the columns of a matrix. In the example that would make v[0] = , v[1] = , and v[2] = Write a definition for get_col_sums. Assume that the matrix it works with has been set up by init_mat, but that the numbers of rows and columns could be any positive integers, not necessarily 2 and 3. Part b is on the next page...

6 ENCM 339 Fall 2017 Section 01 Final Examination page 6 of 9 Part b (6 marks). For the matrix type introduced on the previous page, the save_to_file function is supposed to save a matrix in the binary file format shown to the right of this paragraph. (You may assume for this part that the size of an int is 4 bytes and the size of a double is 8 bytes.) Write a definition for save_to_file. Assume that the matrix the function works with has been set up by init_mat, but that the numbers of rows and columns could be any positive integers, not necessarily 2 and 3. The return value should be 0 for success, 1 for failure to open the file, and 2 if a problem is detected trying to close the file. 8 bytes: m, a, t, r, i, x, 1, 7, 4 bytes: nrow 4 bytes: ncol 8 ncol bytes: row 0 of matrix. 8 ncol bytes: last row of matrix PROBLEM 5 (5 marks). Assume that the calls to malloc succeed in the program given below. In the space beside the program listing, draw a memory diagram for the first time the program gets to point one. #include <stdlib.h> #include <string.h> char **clone(char **p, int n) { char **result = malloc(n * sizeof(char *)); int i, j; for (i = 0; i < n; i++) { result[i] = malloc(strlen(p[i]) + 1); for (j = 0; p[i][j]!= \0 ; j++) { result[i][j] = p[i][j]; // point one result[i][j] = \0 ; return result; char *x[3] = {"ABC", "DE", "F"; char **y; y = clone(x, 3);

7 ENCM 339 Fall 2017 Section 01 Final Examination page 7 of 9 PROBLEM 6 (total of 9 marks). Miscellaneous short-answer questions about Python. Part a (3 marks). The add method of a class will be called if an object of that class is the left operand of the binary + operator, and the radd method of a class will be called if an object of that class is the right operand of the binary + operator. class Weirdo(): def init (self, s1, s2): self.s1 = s1 self.s2 = s2 def str (self): return Weirdo( + self.s1 +, + self.s2 + ) def add (self, rhs): return Weirdo(self.s1 + rhs, self.s2 + rhs) class WeirdoToo(Weirdo): def radd (self, lhs): return WeirdoToo(lhs + self.s1, lhs + self.s2) x = Weirdo( A, B ) y = x + C z = WeirdoToo( D, E ) z = F + z print(x, y, z) print( x a WeirdoToo?, isinstance(x, WeirdoToo)) print( z a Weirdo?, isinstance(z, Weirdo)) What is the output of the above program? Part b (3 marks). Note that attempting to evaluate something like int( xyz ) will raise a ValueError exception. Write the program output in the space beside the program listing. chunks = nope 101 #$%! for c1 in chunks.split(): try: i = int(c1) print( c1 as int:, i) except ValueError: print( not an int:, c1) try: for c2 in chunks.split(): i = int(c2) print( c2 as int:, i) except ValueError: print( not an int:, c2) Part c (3 marks). Write the program output in the space beside the program listing. def addem(x, lo, hi): print( lo =, lo, hi =, hi) if lo + 1 == hi: r = x[lo] else: mid = (lo + hi) // 2 r = addem(x, lo, mid) r += addem(x, mid, hi) print( r =, r) return r a = [5, 7, 11] print( starting... ) s = addem(a, 0, 3) print( done... s =, s)

8 ENCM 339 Fall 2017 Section 01 Final Examination page 8 of 9 PROBLEM 7 (total of 10 marks). In both parts, you do not need to write code to check for invalid parameter types or values. Part a (6 marks). Simpson s rule is an algorithm for finding the approximate value of the definite integral b a f(x)dx, by adding up some weighted values of f(x) for a finite number of evenly-spaced values of x between a and b. A parameter n indicates that n + 1 values of f(x) will be used to make the approximation. The sketch to the right uses n = 6. f(x) a x 1 x 2 x 3 x 4 x 5 b x Given a positive even integer n, the general formula for the approximate integral is ( ) b a ( f(a) + 4f(x 1 ) + 2f(x 2 ) + + 2f(x n 2) + 4f(x n 1) + f(b)) 3n Note that f(x k ) gets multiplied by 4 if k is odd and by 2 if k is even. Complete the following Python function definition. def simpson(f, a, b, n): """Return approximate integral of f(x) from x=a to x=b with parameter n. f must be a function that takes one float argument and return a float. n must be an int that is even and positive.""" Part b (4 marks). Write a Python function called maxcount that has one parameter a non-empty sequence of int values and returns the maximum value for the sequence along with the number of times that value is in the sequence. For example... biggest, howmany = maxcount((1, 7, 7, 6, 7))... should give biggest a value of 7 and howmany a value of 3.

9 ENCM 339 Fall 2017 Section 01 Final Examination page 9 of 9 PROBLEM 8 (9 marks) Joe Student sells bunches of bananas, bags of apples, and bags of oranges to help raise tuition money. Because this is an exam question and not real life, he records his sales in text files that look like this example: 2017 dec 4 10 apples 14 oranges 2017 dec 5 20 oranges 19 bananas 6 apples 2017 dec 6 23 bananas 2017 dec dec 8 16 bananas 22 oranges The first line of the example file indicates that on December 4, 2017, Joe sold 10 bags of apples and 14 bags of oranges, but no bunches of bananas. You can assume that every line of every file has space-separated fields with this organization: The first 3 fields describe a date. The remaining fields are in pairs an integer followed by a type of fruit. Your goal is to write a program to add up total sales in one of these input files. For example, for the above input file, the output should be something like this: 58 bunches of bananas 16 bags of apples 56 bags of oranges Complete the Python program started below. Note that it assumes that the name of the input file will be given by sys.argv[1]. You do not have to write code to check for failure to open the input file or for invalid data in input file. import sys if len(sys.argv)!= 2: print( wrong number of command-line arguments ) sys.exit(1) counts = { apples : 0, bananas : 0, oranges : 0