CSCI-1200/labs/05_vectors

Lab 5 — Vec Implementation

Checkpoint 1

estimate: 20 minutes

• Team up with one student in your lab section. MEET SOMEONE NEW! You may not work with someone who was on your team for Lab 4. Ask a TA or mentor to help you find a partner. If the number of students in the room is not even, the graduate TA will approve a single team with 3 members.
• Introduce yourself to your teammate. Ask them to share something about themselves (e.g. hobbies, sports, favorite music, etc.) Learn something new about your teammate (even if you already know them).

For each function below, assign different letters to each of the data sizes that at first glance might have impact on the running time of the function. Be sure to consider integer value, size of vector, and length of string. Then give the big O notation of the function in terms of those variables.

int foobar (const std::vector<std::string> &a, int b) {
    int answer = 0;
    for (int i = 0; i < a.size(); i+=b) {
        answer++;
    }
    return answer;
}

void foo2 (const std::vector<int> &a, std::string &b) {
    b.clear();
    for (int i = 0; i < a.size(); i++)
    {
        if (a[i] > 0)
            b.push_back('+');
        else
            b.push_back('-');
    }
}

std::vector<int> foo3 (const std::vector<int> &a, const std::string &b) {
    return std::vector<int>(b.size(),a.size());
}

int foo3 (const std::vector<std::string> &a, const std::string& b) {
    int ret = 0;
    for (int i=0; i<a.size(); i++){
        ret += (a[i] == b);
    }
    return ret;
}

std::vector<int> foo4 (const std::vector<int> &a) {
    std::vector<int> answer = a;
    for (int i = 0; i < a.size(); i++) {
        if(a[i] < (a[a.size()-1]*a[a.size()-1])){
            answer.erase(answer.end()-1);
        }
    }
    return answer;
}

std::vector<int> foo5 (const std::vector<int> &a, int b) {
    std::vector<int> ret;
    for(int i=0; i<a.size(); i++){
        if(a[i] < b){
            ret.insert(ret.end(),a[i]);
        }
    }
    return ret;
}

When you finish, discuss these problems with your teammate. If your teammate hasn’t finished, please help them (but without just doing the problems for them).

Once you are both finished, type these examples into your C++ editor, add print statements, and confirm your answers are correct. What print statements will be most helpful? In your terminal, instead of running just ./a.out try running time ./a.out and reading the real time, which is how long your program took to run. How does this change as you increase or decrease each of the data size variables you identified above?

To complete this checkpoint, present your work to a TA/mentor.

Checkpoint 2

estimate: TBD

Write a templated non-member function named remove_matching_elements that takes in two arguments, a vector of type Vec and an element of type T, and returns the number of elements that matched the argument and were successfully removed from the vector. The order of the other elements should stay the same. For example, if v, a Vec object contains 6 elements: 11 22 33 11 55 22 and you call remove_matching_elements(v,11), that call should return 2, and v should now contain: 22 33 55 22. You should not create a new vector in your function. Add several test cases to test_vec.cpp to show that the function works as expected. What is the order notation of your solution in terms of n the size of the vector, and e the number of occurences of the input element in the vector?

To complete this checkpoint, show a TA your debugged solution for remove_matching_elements and be prepared to discuss the order notation of the function.

Checkpoint 3

estimate: TBD

Add a print member function to Vec to aid in debugging. (Note, neither remove_matching_elements nor print are not part of the STL standard for vector). You should print the current information stored in the variables m_alloc, m_size, and m_data. Use the print function to confirm your remove_matching_elements function is debugged. Also, write a test case that calls push_back many, many times (hint, use a for loop!) and observe how infrequently re-allocation of the m_data array is necessary. To verify your code does not contain memory errors or memory leaks, use Valgrind and/or Dr. Memory on your local machine – see instructions on the course webpage: Memory Debugging. Also, submit your code to the homework server (in the practice space for lab 4), which is configured to run the memory debuggers for this exercise. To verify that you understand the output from Valgrind and/or Dr. Memory, temporarily add a simple bug into your implementation to cause a memory error or memory leak.

To complete this checkpoint, show a TA your tested & debugged program. Be prepared to demo and discuss the Valgrind and/or Dr. Memory output: with and without memory errors and memory leaks AND on your local machine and on the homework server.