12.3. Exercises

Many of these exercises are taken from past exams of APS105 Computer Fundamentals courses at University of Toronto. The solutions are provided in the answer boxes.

Headings in this page classify the exercises into different categories: [Easy], [Intermediate], and [Challenging]. I suggest you start by easy exercises and work your way up to the challenging ones.

Question 2 in Winter 2022 Final Exam [Easy]

In a single C statement, define a data structure named Student that has three members: the name of the student as a string (char*), the id of the student as an int, and the grades of the student. The type of the grades of the student is a data structure already defined as follows:

struct marks {
  double labs[10];
  double exams[2];
};

In the same statement, declare one Student variable named test and an array named allStudents of \(500\) Student elements.

Answer

  struct Student {
    char *name;
    int id;
    struct marks grades;
  } test, allStudents[500];

Question 1 in Winter 2020 Final Exam [Easy]

In a single C statement create a data structure called AnimalSizes having two elements, a string name and a size length. This same statement should create an array of this type called snakes with two entries.

Initialize each entry such that the first index has name "Anaconda" and length \(3.7\), while the second index has the name "Python" and length \(2.4\). You may do this in the same statement or using additional statements.

Answer

struct AnimalSizes {
    char name[20];
    double length;
} snakes[2] = {{"Anaconda", 3.7}, {"Python", 2.4}};

Question 7 in Winter 2020 Final Exam [Intermediate]

In various engineering applications, it is required to convert Polar to Cartesian coordinates. The polar coordinates \((R, \theta)\) and rectangular coordinates \((x, y)\) are related as follows:

\[x = R \cos(\theta) \mbox{ and } y = R \sin(\theta) \]

Complete the code below, which defines the data structures and a function that takes polar coordinates of a point and return the rectangular coordinates. The angle is assumed to be in radians. Assuming the values passed to this function is in degrees, you need to convert the radian value using the constant D2R below.

#include <math.h>
const double D2R = 3.1415926535 / 180.0;

// rectangular coordinate structure
typedef struct rectV {



  
}

// polar coordinate structure
typedef struct polarC {  // angle in radians




}

// polar to rectangular
RectCoor polToRec(PolarCoor polin) {




  return rv;
}

Answer

#include <math.h>
const double D2R = M_PI / 180.0;

// rectangular coordinate structure
typedef struct rectV {
  double x;
  double y;
} RectCoor;

// polar coordinate structure
typedef struct polarC {  // angle in radians
  double theta;
  double r;
} PolarCoor;

// polar to rectangular
RectCoor polToRec(PolarCoor polin) {
  RectCoor rv;
  rv.x = polin.r * cos(polin.theta * D2R);
  rv.y = polin.r * sin(polin.theta * D2R);
  return rv;
}

Question 3 in Winter 2018 Final Exam [Intermediate]

Consider the following data structure definition:

typedef struct name {
  char *firstname;
  char *lastname;
} Name;

typedef struct employee {
  int SIN;
  int employeeNumber;
  Name *emplName;
} Empl;

Empl employees[1000];

Assume that all 1000 elements in the employees array have been initialized and none of the pointers are NULL. Write a single C statement that declares a character variable c and assigns it the first character of the last name of the second employee in the employees array.

Answer

The second employee is at index 1, so employees[1].

The name is at employees[1].emplName, which is a pointer to Name structure.

To access the last name of the employee, we can use the arrow operator -> to access the lastname field of the Name structure, employees[1].emplName->lastname.

The first character of the last name is at employees[1].emplName->lastname[0].

char c = employees[1].emplName->lastname[0];

Question 3 in Deferred Exam of Winter 2022 Final Exam [Intermediate]

In the following two lines we create two data structures petal and flower. Write a single C statement that declares a variable named Flower of type struct flower. In the same statement, initialize the name of the Flower to "Rose", the num of petals to 39 and the color of the petals to "red".

struct petal {
  int num;
  char color[25];
};
struct flower {
  char name[25];
  struct petal Petals;
};

Answer

struct flower Flower = {"Rose", {39, "red"}};

Question 5 in Winter 2022 Final Exam [Challenging]

The following C program takes in two names from the user and saves them in the array of data structures students. However, the code does not output the expected output. When the user enters two different last names, the output is the last entered name for both the elements in the array. This is the output of an example run:

Enter last name: Adam
Enter last name: Jones
Jones
Jones

Re-write the getNames function only to have the following output:

Enter last name: Adam
Enter last name: Jones
Adam
Jones

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct student {
  char* lastName;
} Student;
  
void getNames(char* lastName, Student students[]) {
  for (int i = 0; i < 2; i++) {
    printf("Enter last name: ");
    scanf("%s", lastName);
    students[i].lastName = lastName;
  }
}
  
int main() {
  Student students[2];
  
  char* lastName = malloc(sizeof(char) * 20);
  getNames(lastName, students);
  
  for (int i = 0; i < 2; i++) {
    printf("%s\n", students[i].lastName);
  }
  free(lastName);
  lastName = NULL;
  return 0;
} 

Answer

void getNames(char* lastName, Student students[]) {
  for (int i = 0; i < 2; i++) {
    printf("Enter last name: ");
    scanf("%s", lastName);
    students[i].lastName = (char*) malloc(sizeof(char) * 20); // allocate memory for the string
    strcpy(students[i].lastName, lastName);
  }
}