Question 1

In a multi-threaded C++ program, why would you use a mutex?

Accepted Answer

To protect shared resources from concurrent access

Question 2

What is the difference between int* arr and int arr[] in function parameters?

Accepted Answer

There is no difference; both are treated as pointers

Question 3

Consider the following code:
int x = 5;
int* ptr = &x;
*ptr = 10;
After execution, what is the value of x?
a) 5
b) 10
c) Undefined
d) Compiler error

Accepted Answer

10

Question 4

In your threaded bubble sort program, total_swaps is a global variable. Why is a mutex needed when updating it?

Accepted Answer

To ensure only one thread updates it at a time

Question 5

Which of the following is stored on the heap?
a) Global variables
b) Local variables in a function
c) Dynamically allocated arrays using new
d) Function parameters

Accepted Answer

Dynamically allocated arrays using new

Question 6

What is the output of the following code?
#include <iostream>
using namespace std;
void swap(int &x, int y) { int temp = x;  
x = y;  
y = temp;}
int main() {
    int a = 10, b = 20;
    swap(a, b);
    cout << a << ',' << b << endl; return 0;
}

Accepted Answer

10,20

Question 7

Which function would you use to copy a null-terminated character array?
a) strcpy(dest, src);
b) strncpy(dest, src);
c) strlen(dest);
d) Both a and b

Accepted Answer

Both a and b

Question 8

Which statement about threads in C++ is true?
a) Threads automatically synchronize without any additional code
b) Each thread gets its own stack, but shares the heap
c) Threads cannot access global variables
d) Threads cannot be joined

Accepted Answer

Each thread gets its own stack, but shares the heap

Question 9

What is the difference between the stack and heap?

Accepted Answer

Stack is local memory with automatic cleanup; heap requires manual allocation and deletion

Question 10

In your project, why did you pass int* start and int size to each thread for sorting?

Accepted Answer

To ensure threads operate on separate sections of the array

Question 11

int showElement(int A[], int index)
{
    cout << A[index];
}

Which of the answers will print the same correct output? 
a) cout << *(A + index); 
b) cout << &A[index];
c) cout << *A + index;
d) cout << &A + index;

Accepted Answer

cout << *(A + index);

Question 12

Assume the following C++ code segment:
struct student{
    string name;
    int age;
    char grade;
};
student s1, *sptr;
sptr = &s1;
s1.name = "MasterGold";

What code would you use to set MasterGold's age to 49?

Accepted Answer

sptr->age = 49;

Question 13

Assume the same C++ code as above. What code would you use to set MasterGold's grade to 'A'?
a) The correct answer is not listed 
b) sptr.grade = 'A';
c) s1->grade = 'A';
d) MasterGold->grade = 'A';

Accepted Answer

The correct answer is not listed.
You would use s1.grade = 'A'; or sptr->grade = 'A';

Question 14

In which C++ library is strlen() found? a) b) The correct answer is not listed. c) d)

Accepted Answer

Question 15

Consider the following valid C++ function:
void func(char * ptr)
{
    cout << ptr;
}

What is the passing mode used in the function to pass the parameter ptr?
a) pass by reference
b) pass by touchdown
c) pass by linkage
d) pass by value

Accepted Answer

pass by value

Question 16

What is another name for a "null terminated character array"?
a) The correct answer is not listed
b) container
c) word
d) C-string

Accepted Answer

C-string

Question 17

char name[15] = "PonyExpress"; 
char * cptr = name;
 name = "cowboy"; 
cout << name;

What is wrong here?

Accepted Answer

You can't assign "cowboy" to name

Question 18

The function pthread_create() has how many parameters?
a) 4 
b) 1
c) 2
d) 3

Accepted Answer

4

Question 19

Consider the following C++ code segment:
char word[10] = "matrix";
cout << strlen(word);

What will be printed to the screen?
a) 10
b) matrix
c) The correct answer is not listed
d) 6

Accepted Answer

6

Question 20

The function pthread_create() allows a program to have multiple threads running concurrently.
a) True 
b) False

Accepted Answer

True

Question 21

What is the time complexity of the following C++ code segment?
for (int i = 0; i < N; i++) {
    for (int j = 0; j < N; j++) {
        cout << i + j << endl;
    }
}
a) O(N)
b) O(log N)
c) O(N^2)
d) O(N log N)

Accepted Answer

O(N^2)

Question 22

What is the worst-case time complexity of Bubble Sort for an array of size N?
a) O(N)
b) O(N log N)
c) O(N^2)
d) O(log N)

Accepted Answer

O(N^2)

Question 23

What is the best-case time complexity of Bubble Sort if the array is already sorted?
a) O(N)
b) O(N^2)
c) O(log N)
d) O(1)

Accepted Answer

O(N)

Question 24

What is the time complexity of accessing an element in a C++ array by index?
a) O(N)
b) O(log N)
c) O(1)
d) O(N^2)

Accepted Answer

O(1)

Question 25

Which of the following Big-O notations best describes the time complexity of merging two sorted arrays of size N each?
a) O(N)
b) O(N^2)
c) O(log N)
d) O(N log N)

Accepted Answer

O(N)

Question 26

Consider the mysort.cpp project using multiple threads to sort segments of an array. If each segment is of size N/S, and there are S segments, what is the Big-O time complexity for sorting all segments using Bubble Sort in the worst case?

Accepted Answer

O(N^2)

Question 27

In your mysort.cpp project, the bubble sort function needs ____ parameters.

Accepted Answer

3

Question 28

When sorting a vector, how many parameters does the bubblesort() function need?

Accepted Answer

1

Question 29

How many parameters does the bubbleSort() function need?

Accepted Answer

2

Question 30

What is the expected growth rate of bubbleSort algorithm?

Accepted Answer

O(N^2) or O(N*N)

Question 31

Which sorting algorithm is the fastest of those listed:
- Bubble sort
- Insertion sort
- Selection sort

Accepted Answer

The listed algorithms are all about the same because they are all n-squared sort

Question 32

What Linux command is used to generate information about memory usage?

Accepted Answer

Free

Question 33

int* ptr = new int;
*ptr = 42;

What is true about the variable ptr?

Accepted Answer

ptr stores the address of a dynamically allocated integer on the heap

Question 34

int arr[5] = {10, 20, 30, 40, 50};
int *ptr = arr;
cout << *(ptr + 2) << endl;

What is printed to the screen?
a) 10
b) 20
c) 30
d.)40

Accepted Answer

30

Question 35

Consider a variable declared as static int count = 0; inside a function.
Which statement is correct?
a) count is reset to 0 every time the function is called.
b) count retains its value between function calls but is not visible outside the function

Accepted Answer

count retains its value between function calls but is not visible outside the function

Question 36

In the bubble() function, the variable num_swaps is local. 
Which of the following is true?
a) Its value persists between calls to bubble() 
b) Each thread has its own separate num_swaps count.
c) It must be declared as static to count swaps correctly

Accepted Answer

Each thread has its own separate num_swaps count

Question 37

Which of the following statements about the global variable total_swaps in your threaded sort program is correct?
a. It is only accessible inside the bubble() function
b. It retains its value for the entire program and can be accessed by all threads

Accepted Answer

It retains its value for the entire program and can be accessed by all threads.

Question 38

Why is a mutex used in the threaded bubble() function in your sort program?

Accepted Answer

To prevent multiple threads from updating total_swaps at the same time.

Question 39

Which of the following statements correctly locks and unlocks a mutex?
a) locker.unlock(); locker.lock();
b) locker.lock(); // critical section locker.unlock();
c) lock(locker);
d) mutex.locked(); mutex.unlocked();

Accepted Answer

locker.lock(); //critical section locker.unlock();

Question 40

What could happen if total_swaps was incremented by multiple threads without using a mutex?
a. Nothing, it would still count correctly.
b. The program would crash immediately.
c. The total swap count could be incorrect due to race conditions.

Accepted Answer

The total swap count could be incorrect due to race conditions

Question 41

In your program, mutex locker; is declared globally. Why?

Accepted Answer

So all threads can access the same mutex to coordinate access to total_swaps

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CECS 325 Quiz 4 Gold