priorityqueue6.cpp

This is the second part of that lab manual to teach you how to make real-time programme and how to d

//: C07:PriorityQueue6.cpp
// From "Thinking in C++, 2nd Edition, Volume 2"
// by Bruce Eckel & Chuck Allison, (c) 2001 MindView, Inc.
// Available at www.BruceEckel.com.
//{L} ../TestSuite/Test
#include <iostream>
#include <queue>
#include <algorithm>
#include <cstdlib>
#include <ctime>
using namespace std;

template<class T, class Compare>
class PQV : public vector<T> {
  Compare comp;
  bool sorted;
  void assureHeap() {
    if(sorted) {
      // Turn it back into a heap:
      make_heap(begin(), end(), comp);
      sorted = false;
    }
  }    
public:
  PQV(Compare cmp = Compare()) : comp(cmp) {
    make_heap(begin(), end(), comp);
    sorted = false;
  }
  const T& top() {
    assureHeap();
    return front(); 
  }
  void push(const T& x) {
    assureHeap();
    // Put it at the end:
    push_back(x);
    // Re-adjust the heap:
    push_heap(begin(), end(), comp);
  }
  void pop() {
    assureHeap();
    // Move the top element to the last position:
    pop_heap(begin(), end(), comp);
    // Remove that element:
    pop_back();
  }
  void sort() {
    if(!sorted) {
      sort_heap(begin(), end(), comp);
      reverse(begin(), end());
      sorted = true;
    }
  }
};

int main() {
  PQV<int, less<int> > pqi;
  srand(time(0));
  for(int i = 0; i < 100; i++) {
    pqi.push(rand() % 25);
    copy(pqi.begin(), pqi.end(),
      ostream_iterator<int>(cout, " "));
    cout << "\n-----\n";
  }
  pqi.sort();
  copy(pqi.begin(), pqi.end(),
    ostream_iterator<int>(cout, " "));
  cout << "\n-----\n";
  while(!pqi.empty()) {
    cout << pqi.top() << ' ';
    pqi.pop();
  }
} ///:~