优先队列排序不正确

Question

I am trying to code a computer scheduling system with c++. I am using an array-based priority queue. This is the idea of the program

Each input transaction will represent a new computer repair order to be scheduled or a “service” command. A new computer repair order will be represented in three parts separated by hyphens: customer ID (variable length), computer model year (4 digits), warranty code (y or n). Each repair order will be scheduled based on priority and the order in which the repair order was received (first-come-first-served). A warranty repair order (ie, warranty code = 'y') is assigned priority 1 (highest). A non-warranty repair for a computer model less than 6 years old is assigned priority 2. A non-warranty repair order for a computer model older than 5 years is assigned a priority 3 (lowest). Each repair order is placed in a priority queue and will be serviced by the next available repair technician. A transaction that contains a “service” command results in a repair order being removed from the priority queue and the customer ID being displayed on the console. A transaction containing the string “end-of-file” will signal the end of the input. Display the number of repair orders remaining in the queue when the “end-of-file” transaction is processed.

Here is the input I used:

anna-2019-y
james-2012-y
jill-2008-y

The output when I enter the "service" command is

service
jill-2008-y
service
anna-2019-y
service
james-2012-y

but the correct output should be

service
anna-2019-y
service
james-2012-y
service
jill-2008-y

This is my code:

#include <iostream>
#include <cmath>

using namespace std;

class heapType{
  public:
    bool empty(); 
    void service();
    void pop();
    void push(string cus);
    int remain();
    heapType();

  private:
    int C1I;
    int C2I;
    int CI;
    int done; 
    int EOL;
    int count;
    string heap[10];
    int PI;

    void swap(int I1, int I2);
};

bool heapType::empty() {
    return (count == 0);
}

int heapType::remain() {
    return count;
}

void heapType::swap(int I1, int I2) {
    string T = heap[I1];
    heap[I1] = heap[I2];
    heap[I2] = T;
}

void heapType::service() {
    if (count == 0) {
    }
    else {
        string name = heap[0];
        int pos1 = heap[0].find('-');
        int pos2 = heap[0].find('-', pos1 + 1);
        cout << "(output: " << heap[0].substr(pos2 + 1) << ")" << endl;
    }
}

heapType::heapType() {  
    EOL = 0;
    count = 0;
    for (int i = 0; i < 10; i++)
        heap[i] = "0";
}

void heapType::push(string cus){
    if (count == 10){
        cout << "Error: queue is full." << endl;
    }
    else {
        count++;
        heap[EOL] = cus;
        CI = EOL;
        EOL++;
        done = 0;
        while (!done) {
            if (CI == 0)
                done = 1;
            else {
                PI = (CI - 1) / 2;
                if (heap[PI] <= heap[CI])
                    done = 1;
                else{
                    swap(PI, CI);
                    CI = PI;
                }
            }
        }
    }
}

string change(string choice){
    string newExpression;
    int p1, p2, intYear;
    string name, year, priority, warranty;
    static int seq = 1;
    string sequence;

    p1 = choice.find('-');
    p2 = choice.find('-', p1 + 1);
    name = choice.substr(0, p1);
    warranty = choice.substr(p2 + 1);
    year = choice.substr(p1 + 1, p2 - p1 - 1);
    intYear = atoi(year.c_str());
    if (warranty == "y")
        priority = "1";
    else if (2019 - intYear < 6)
        priority = "2";
    else
        priority = "3";
    newExpression = priority + "-" + sequence + "-" + name;
    seq++;
    return newExpression;
}

void heapType::pop() {
    if (count == 0)
        cout << "Error: queue is empty.\n";
    else {
        if (count == 1) {
            count = 0;
            EOL = 0;
            heap[0] = "0";
        }
        else {
            if (count == 2) {
                count = 1;
                EOL = 1;
                heap[0] = heap[1];
                heap[1] = "0";
            }
            else {
                count--;
                EOL--;
                heap[0] = heap[EOL];
                heap[EOL] = "0";
                done = 0;
                PI = 0;
                C1I = 1;
                C2I = 2;
                while (!done){
                    if (C2I >= EOL){
                        if (heap[PI] > heap[C1I])
                            swap(PI, C1I);
                        done = 1;
                    }
                    else {
                        if((heap[PI] <= heap[C1I]) && (heap[PI] <= heap[C2I]))
                            done = 1;
                        else {
                            if (heap[C1I] < heap[C2I]) {
                                swap(PI, C1I);
                                if ((C1I * 2 + 1) >= EOL)
                                    done = 1;
                                else
                                    PI = C1I;
                            } else {
                                swap(PI, C2I);
                                if ((C2I * 2 + 1) >= EOL)
                                    done = 1;
                                else
                                    PI = C2I;
                            }
                            C1I = PI * 2 + 1;
                            C2I = PI * 2 + 2;
                        }
                    }
                }
            }
        }
    }
}

int main(){
  heapType iHeap;
  string choice, second;

  cout << "\nInput transaction(customerid-year-warrantycode)\n";
  cout << "Service(service)\n";
  cout << "Exit program(end-of-file)\n";
  cin >> choice;

  while (choice != "end-of-file"){
    if (choice == "service"){
      iHeap.service();
      iHeap.pop();
    }
    else {
      second = change(choice);
      iHeap.push(second);
    }
    cout << "\nInput transaction(customerid-year-warrantycode)\n";
    cout << "Service(service)\n";
    cout << "Exit program(end-of-file)\n";
    cin >> choice;
  }
  cout << "(output: There are " << iHeap.remain()
       << " remaining repair orders in the queue)";
  return 0;
}

Answer 1

The problem is in your change function, which computes the priority and then constructs a new priority expression with this line:

newExpression = priority + "-" + sequence + "-" + name;

But you never assign it a value, so likely it's NULL . Is your compiler issuing a warning about this? The output from this function will be a string of the form priority--name .

Given your sample input (from comments), I've created this table to show the expressions you'll compute:

jim-2001-y      1--jim
jake-2012-y     1--jake
frank-2011-y    1--frank
james-2019-y    1--james

They're all the same priority and you don't have a sequence number, so they're going to be sorted alphabetically.