Question

This is the requirement: whenever a new word is encountered, the program should allocate an instance of the node from dynamic memory to contain the word and its count and insert it into a linked list so that the list is always sorted. If the word encountered already exists in the list, then the count for that word should be incremented.

I did search everywhere and the proper solution is using std::map, but I dont want to use that because I haven’t learnt that so far. Is it alright to use List or Vector and create a struct or class to manipulate each node ?

This is my proper code

class Node {
string word;
int count;

public:
    Node() {
        word = "";
        count = 1;
    }
    Node(const Node &other) : word(other.word), count(other.count) {
        // copy constructor 
    }
    ~Node() {} // Destructor

    void printWord() const {
        cout << count << " " << word << endl;
    }
    void loadWord(ifstream &fin) { 
        fin >> word;
    }
    void setWord(const string &word) {
        this->word = word;
    }
    const string& getWord() const {
        return word;
    }
    void incrementCount() {
        count++;
    }
};

void load(list<Node> &nodes, const char *file);
void print(const list<Node> &nodes);
bool isExist(const list<Node> &nodes, const string &word, Node &node);
void error(const string &message, const char *file);
const Node& getNode(const list<Node> &nodes, const string &word);

int main(int argc, char *argv[]) {

    list<Node> nodes;

    if (argc != 2) {
        cout << "Error syntax : require an input file\n";
        return 0;
    }
    load(nodes, argv[1]);
    print(nodes);

    return 0;   
}

void print(const list<Node> &nodes) {

    list<Node>::const_iterator itr;

    for (itr = nodes.begin(); itr != nodes.end(); itr++) {
        itr->printWord();
    }
cout << '\n';
}

void load(list<Node> &nodes, const char *file) { 

    ifstream fin;
    Node node;
    string temp;

fin.open(file);

if (!fin) 
    error("Cannot open file ", file); // exit

while (!fin.eof()) {
    if (fin.good()) {
        fin >> temp;
        if (!isExist(nodes, temp, node)) {
            node.setWord(temp);
            nodes.push_back(node);
        } else {
            // increase word count here
        }

    } else if (!fin.eof()) 
        error("Unable to read data from ", file);
}
fin.close();
}

bool isExist(const list<Node> &nodes, const string &word, Node &node) {
list<Node>::const_iterator itr;
for (itr = nodes.begin(); itr != nodes.end(); itr++) {
    if(word.compare(itr->getWord()) == 0) {
        return true;
    }
}
return false;
}

const Node& getNode(const list<Node> &nodes, const string &word) {
    list<Node>::const_iterator itr;
    for (itr = nodes.begin(); itr != nodes.end(); itr++) {
        if(word.compare(itr->getWord()) == 0) {
            return *itr;
        }
    }
    return NULL; // This is fail what should I do to return a NULL value when not found
}

void error(const string &message, const char *file) {
cerr << message << file << '\n';
exit(0);
}

The code doesn’t work, I just tried to generate my solution to solve the question by applying my Java knowledge but it seems diffirent to control object in c++. Could someone examine my code and suggest me a better way ?

Thanks.

Answer 1

No, this is not the best task to practice vectors and lists. You really have to look at std::map documentation and write 3 lines of efficient, nice looking code.
Why didn’t you apply your TreeMap Java knowledge?