Question

C++

Implement the removeBad function:

        #include <list>
        #include <vector>
        #include <algorithm>
        #include <iostream>
        #include <cassert>
        using namespace std;

        vector<int> destroyedOnes;

        class Movie
        {
          public:
            Movie(int r) : m_rating(r) {}
            ~Movie() { destroyedOnes.push_back(m_rating); }
            int rating() const { return m_rating; }
          private:
            int m_rating;
        };

          // Remove the movies in li with a rating below 50 and destroy them.
          // It is acceptable if the order of the remaining movies is not
          // the same as in the original list.
        void removeBad(list<Movie*>& li)
        {
        }

        void test()
        {
            int a[8] = { 85, 80, 30, 70, 20, 15, 90, 10 };
            list<Movie*> x;
            for (int k = 0; k < 8; k++)
                x.push_back(new Movie(a[k]));
            assert(x.size() == 8 && x.front()->rating() == 85 && x.back()->rating() == 10);
            removeBad(x);
            assert(x.size() == 4 && destroyedOnes.size() == 4);
            vector<int> v;
            for (list<Movie*>::iterator p = x.begin(); p != x.end(); p++)
            {
                Movie* mp = *p;
                v.push_back(mp->rating());
            }
              // Aside:  In C++11, the above loop could be
              //     for (auto p = x.begin(); p != x.end(); p++)
              //     {
              //         Movie* mp = *p;
              //         v.push_back(mp->rating());
              //     }
              // or    
              //     for (auto p = x.begin(); p != x.end(); p++)
              //     {
              //         auto mp = *p;
              //         v.push_back(mp->rating());
              //     }
              // or    
              //     for (Movie* mp : x)
              //         v.push_back(mp->rating());
              // or    
              //     for (auto mp : x)
              //         v.push_back(mp->rating());
            sort(v.begin(), v.end());
            int expect[4] = { 70, 80, 85, 90 };
            for (int k = 0; k < 4; k++)
                assert(v[k] == expect[k]);
            sort(destroyedOnes.begin(), destroyedOnes.end());
            int expectGone[4] = { 10, 15, 20, 30 };
            for (int k = 0; k < 4; k++)
                assert(destroyedOnes[k] == expectGone[k]);
            for (list<Movie*>::iterator p = x.begin(); p != x.end(); p++)
                delete *p;  // Deallocate remaining movies.
        }

        int main()
        {
            test();
            cout << "Passed" << endl;
        }

For this problem, you will turn a file named bad.cpp with the body of the removeBad function, from its "void" to its "}", no more and no less. Your function must compile and work correctly when substituted into the program above.

Answer 1

C++ Code:

#include <list>
#include <vector>
#include <algorithm>
#include <iostream>
#include <cassert>
using namespace std;

vector<int> destroyedOnes;

class Movie
{
public:
Movie(int r) : m_rating(r) {}
~Movie() { destroyedOnes.push_back(m_rating); }
int rating() const { return m_rating; }
private:
int m_rating;
};

// Remove the movies in li with a rating below 50 and destroy them.
// It is acceptable if the order of the remaining movies is not
// the same as in the original list.
void removeBad(list<Movie*>& li)
{   
//iterate through list
for(list<Movie*>::iterator it=li.begin();it!=li.end();){
if((*it)->rating()<50){//if rating less than 50
Movie *movie=*it;//retrive the movie
it=li.erase(it);//erase from list move to next iterator
delete movie;//delete the removed movie
}else{
++it;//move to next element
}
}
}

void test()
{
int a[8] = { 85, 80, 30, 70, 20, 15, 90, 10 };
list<Movie*> x;
for (int k = 0; k < 8; k++)
x.push_back(new Movie(a[k]));
assert(x.size() == 8 && x.front()->rating() == 85 && x.back()->rating() == 10);
removeBad(x);
assert(x.size() == 4 && destroyedOnes.size() == 4);
vector<int> v;
for (list<Movie*>::iterator p = x.begin(); p != x.end(); p++)
{
Movie* mp = *p;
v.push_back(mp->rating());
}
// Aside: In C++11, the above loop could be
// for (auto p = x.begin(); p != x.end(); p++)
// {
// Movie* mp = *p;
// v.push_back(mp->rating());
// }
// or
// for (auto p = x.begin(); p != x.end(); p++)
// {
// auto mp = *p;
// v.push_back(mp->rating());
// }
// or
// for (Movie* mp : x)
// v.push_back(mp->rating());
// or
// for (auto mp : x)
// v.push_back(mp->rating());
sort(v.begin(), v.end());
int expect[4] = { 70, 80, 85, 90 };
for (int k = 0; k < 4; k++)
assert(v[k] == expect[k]);
sort(destroyedOnes.begin(), destroyedOnes.end());
int expectGone[4] = { 10, 15, 20, 30 };
for (int k = 0; k < 4; k++)
assert(destroyedOnes[k] == expectGone[k]);
for (list<Movie*>::iterator p = x.begin(); p != x.end(); p++)
delete *p; // Deallocate remaining movies.
}

int main()
{
test();
cout << "Passed" << endl;
}

output:

sh-4.2$ gt+ -o main *.cpp sh-4.2$ main Passed sh-4.2$