12.16. Activecode Exercises

Answer the following Activecode questions to assess what you have learned in this chapter.

Question

Let's write the struct definition for song. song should have instance variables title, artist, and num_likes.

Example c192_mucp_12_1_ac_q

#include <iostream>
// YOUR CODE HERE

Answer

Below is one way to define the song struct.

Example c192_mucp_12_1_ac_a

#include <cstddef>
#include <string>
#include <iostream>

struct song {
    std::string title;
    std::string artist;
    std::size_t num_likes;
};

Question

Let's make an album! Write the struct definition for album, which should have instance variables name, year and a vector of Songs.

Example c192_mucp_12_2_ac_q

#include <iostream>
#include <vector>
// YOUR CODE HERE

Answer

Below is one way to define the album struct.

Example c192_mucp_12_2_ac_a

#include <cstddef>
#include <string>
#include <iostream>
#include <vector>

struct song {
    std::string title;
    std::string artist;
    std::size_t num_likes;
};

struct album {
    std::string name;
    int year;
    std::vector<song> songs;
};

Question

Two Songs are equal if the title and artist of the Songs are equal. Write the function song_equal, which takes two Songs as parameters and returns true if they are equal.

Example c192_mucp_12_3_ac_q

#include <iostream>

// YOUR CODE HERE

Answer

Below is one way to write the song_equal function.

Example c192_mucp_12_3_ac_a

#include <cstddef>
#include <string>
#include <iostream>

struct song {
    std::string title;
    std::string artist;
    std::size_t num_likes;
};

bool song_equal (const song& a, const song& b) {
    if (a.title == b.title && a.artist == b.artist) {
        return true;
    }
    else {
        return false;
    }
}

Question

What if we'd like to search an album for our favorite song? Write the album member function search_album which takes a song as a parameter and returns the location of the song in the album. If the song isn't found, return -1. Use the song_equal function we defined earlier!

Example c192_mucp_12_4_ac_q

#include <iostream>
#include <vector>
// YOUR CODE HERE

Answer

Below is one way to write the album member function.

Example c192_mucp_12_4_ac_a

#include <cstddef>
#include <string>
#include <iostream>
#include <vector>

struct song {
    std::string title;
    std::string artist;
    std::size_t num_likes;
};

struct album {
    std::string name;
    int year;
    std::vector<song> songs;
public:
    std::ptrdiff_t search_album(const song& a);
};

std::ptrdiff_t album::search_album (const song& a) {
    for (std::size_t i = 0; i < songs.size(); ++i) {
        if ((songs[i].title == a.title && songs[i].artist == a.artist)) {
            return static_cast<std::ptrdiff_t>(i);
        }
    }
    return -1;
}

Question

What's the most popular song within an album? Let's write the album member function most_liked_song, which prints out the information of the most liked song in the format "The most liked song is title by artist with num_likes likes."

Example c192_mucp_12_5_ac_q

#include <iostream>
#include <vector>
// YOUR CODE HERE

Answer

Below is one way to write the album member function.

Example c192_mucp_12_5_ac_a

#include <cstddef>
#include <string>
#include <iostream>
#include <vector>
using std::cout;

struct song {
    std::string title;
    std::string artist;
    std::size_t num_likes;
};

struct album {
    std::string name;
    int year;
    std::vector<song> songs;
public:
    void most_liked_song();
};

void album::most_liked_song () {
    if (songs.empty()) { cout << "The album is empty.\n"; return; }
    std::size_t max_index = 0;
    std::size_t max_likes = 0;
    for (std::size_t i = 0; i < songs.size(); ++i) {
        if (songs[i].num_likes > max_likes) {
            max_index = i;
            max_likes = songs[i].num_likes;
        }
    }
    cout << "The most liked song is " << songs[max_index].title;
    cout << " by " << songs[max_index].artist << " with ";
    cout << songs[max_index].num_likes << " likes." << std::endl;
}

Question

Let's write the struct definition for product. product should have instance variables name and price.

Example c192_mucp_12_6_ac_q

#include <iostream>
// YOUR CODE HERE

Answer

Below is one way to define the product struct.

Example c192_mucp_12_6_ac_a

#include <string>
#include <iostream>

struct product {
    std::string name;
    double price;
};

Question

Let's make a shopping list! Write the struct definition for list, which should have instance variables type and a vector of Products.

Example c192_mucp_12_7_ac_q

#include <iostream>
#include <vector>
// YOUR CODE HERE

Answer

Below is one way to define the list struct.

Example c192_mucp_12_7_ac_a

#include <string>
#include <iostream>
#include <vector>

struct product {
    std::string name;
    double price;
};

struct list {
    std::string type;
    std::vector<product> products;
};

Question

Two Products are equal if the name and price of the Products are equal. Write the function product_equal, which takes two Products as parameters and returns true if they are equal. What if we want to check to see if we have bananas in our shopping list? Write the list member function search_list, which takes a product as a parameter and returns the location of the product in the list. Return -1 if it's not in the list.

Example c192_mucp_12_8_ac_q

#include <iostream>
#include <vector>
// YOUR CODE HERE

Answer

Below is one way to write the search_list member function.

Example c192_mucp_12_8_ac_a

#include <cstddef>
#include <string>
#include <iostream>
#include <vector>

struct product {
    std::string name;
    double price;
};

bool product_equal (const product& a, const product& b) {
    if (a.name == b.name && a.price == b.price) {
        return true;
    }
    else {
        return false;
    }
}

struct list {
    std::string type;
    std::vector<product> products;
    std::ptrdiff_t search_list(const product& a);
};

std::ptrdiff_t list::search_list (const product& a) {
    for (std::size_t i = 0; i < products.size(); ++i) {
        if (product_equal (products[i], a)) {
            return static_cast<std::ptrdiff_t>(i);
        }
    }
    return -1;
}

Question

Time to checkout! Write the list member function total_price which calculates and returns the total price of all the Products.

Example c192_mucp_12_9_ac_q

#include <iostream>
#include <vector>
// YOUR CODE HERE

Answer

Below is one way to write the total_price member function.

Example c192_mucp_12_9_ac_a

#include <cstddef>
#include <string>
#include <iostream>
#include <vector>

struct product {
    std::string name;
    double price;
};

struct list {
    std::string type;
    std::vector<product> products;
public:
    double total_price();
};

double list::total_price () {
    double total = 0;
    for (std::size_t i = 0; i < products.size(); ++i) {
        total += products[i].price;
    }
    return total;
}

Question

Oops! We made a mistake and grabbed pineapple pizza. What if we want to remove an product from our list? Write the list member function remove_product, which takes an index as a parameter and removes it. Then it fills the gap with the last product in the list.

Example c192_mucp_12_10_ac_q

#include <iostream>
#include <vector>
// YOUR CODE HERE

Answer

Below is one way to write the remove_product member function.

Example c192_mucp_12_10_ac_a

#include <stdexcept>
#include <cstddef>
#include <string>
#include <iostream>
#include <vector>

struct product {
    std::string name;
    double price;
};

struct list {
    std::string type;
    std::vector<product> products;
public:
    void remove_product(std::size_t index);
};

void list::remove_product (std::size_t index) {
    if (index >= products.size()) throw std::out_of_range("product index");
    products[index] = products.back();
    products.pop_back();
}