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#ifndef PRIORITY_QUEUE_HPP
#define PRIORITY_QUEUE_HPP
#include <iostream>
template<typename T>
class PriorityQueue {
public:
// creates a new object of type T
PriorityQueue();
// deletes the array priority_array so that there are no memory leaks
~PriorityQueue();
// pushes element to the queue which is sorted by smallest element first
void push(const T& element);
// pops the first element from the queue and removes it while returning
// it
T pop();
// returns the lowest priority item
T get_first();
// check if item is in queue
bool check_item(const T& item);
// gets index of item
int get_index(const T& item);
// removes item from queue
void remove_item(const T& item);
void clear();
// return element at position;
const T& at(const unsigned int& i) const;
const T& operator[](const unsigned int& i) const;
private:
// size of the current queue
unsigned int size;
// capacity of the queue, this will just increase in multiples of 2
unsigned int capacity;
// array that will represent the priority queue
T *priority_array;
// resize the queue's array accordingly by some factor
void resize_queue(double factor);
// insert and element into the queue
// this assumes that the capacity is larger than the size
void insert_queue(const T& element, const unsigned int& loc);
// removes an element from the queue
T remove_queue(const unsigned int& loc);
};
template<typename T>
PriorityQueue<T>::PriorityQueue() : size(0), capacity(1) {
priority_array = new T;
}
template<typename T>
PriorityQueue<T>::~PriorityQueue() {
delete[] priority_array;
}
template<typename T>
void PriorityQueue<T>::push(const T& element) {
unsigned int insert_loc = 0;
if(size == capacity)
resize_queue(2);
while(insert_loc < size && element > priority_array[insert_loc])
++insert_loc;
insert_queue(element, insert_loc);
}
template<typename T>
T PriorityQueue<T>::pop() {
if(!size)
throw "Priority Queue is empty, no item to pop";
else if(size == capacity / 2)
resize_queue(0.5);
T tmp = remove_queue(0);
return tmp;
}
template<typename T>
T PriorityQueue<T>::get_first() {
return priority_array[0];
}
template<typename T>
bool PriorityQueue<T>::check_item(const T& item) {
for(unsigned int i = 0; i < size; ++i)
if(priority_array[i] == item)
return true;
return false;
}
template<typename T>
int PriorityQueue<T>::get_index(const T& item) {
for(unsigned int i = 0; i < size; ++i)
if(priority_array[i] == item)
return i;
return -1;
}
template<typename T>
void PriorityQueue<T>::remove_item(const T& item) {
remove_queue(get_index(item));
}
template<typename T>
void PriorityQueue<T>::clear() {
T *tmp = new T;
size = 0;
capacity = 1;
delete[] priority_array;
priority_array = tmp;
}
template<typename T>
const T& PriorityQueue<T>::at(const unsigned int& i) const {
return priority_array[i];
}
template<typename T>
const T& PriorityQueue<T>::operator[](const unsigned int& i) const {
return priority_array[i];
}
template<typename T>
void PriorityQueue<T>::resize_queue(double factor) {
capacity = (double)capacity * factor;
T *tmp_array = new T[capacity];
for(unsigned int i = 0; i < size; ++i)
tmp_array[i] = priority_array[i];
delete[] priority_array;
priority_array = tmp_array;
}
template<typename T>
void PriorityQueue<T>::insert_queue(const T& element, const unsigned int& loc) {
T *tmp_array = new T[capacity];
for(unsigned int i = 0; i < size + 1; ++i)
if(i == loc)
tmp_array[i] = element;
else if(i < loc)
tmp_array[i] = priority_array[i];
else
tmp_array[i] = priority_array[i - 1];
size++;
delete[] priority_array;
priority_array = tmp_array;
}
template<typename T>
T PriorityQueue<T>::remove_queue(const unsigned int& loc) {
T element;
T *tmp_array = new T[capacity];
for(unsigned int i = 0; i < size; ++i)
if(i == loc)
element = priority_array[i];
else if(i < loc)
tmp_array[i] = priority_array[i];
else
tmp_array[i - 1] = priority_array[i];
size--;
delete[] priority_array;
priority_array = tmp_array;
return element;
}
#endif // PRIORITY_QUEUE_HPP
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