Priority Queue

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

template <class T>
class PriorityQueue{
private:
    vector<T> heap;
    int size = 0;

    int getLeft(int index) const {return index * 2 + 1;}
    int getRight(int index) const {return index * 2 + 2;}
    int getParent(int index) const {return (index + 1) / 2 - 1;}

    void heapify(int index){
        int left = getLeft(index),
            right = getRight(index),
            min = index;

        if(left < size && heap[left] < heap[min])
            min = left;
        if(right < size && heap[right] < heap[min])
            min = right;

        if(min != index){
            swap(heap[min], heap[index]);
            heapify(min);
        }
    }
public:
    //c-tors & d-tor
    PriorityQueue() = default;
    PriorityQueue(int size) : heap(size){}
    ~PriorityQueue() = default;

    void enqueue(T item){
        //Check if there is enough room in vector
        if(heap.size() >= ++size){
            heap[size - 1] = item;
        }else{
            heap.push_back(item);
        }

        //bubble up to correct position in heap
        int curr = size - 1, parent = getParent(curr);

        while(curr != 0 && heap[curr] < heap[parent]){
            swap(heap[curr], heap[parent]);
            curr = parent;
            parent = getParent(curr);
        }
    }

    T dequeue(){
        T temp = heap[0];

        swap(heap[0], heap[--size]);
        heapify(0);

        return temp;
    }

};

int main(){
    PriorityQueue<int> p;

    p.enqueue(4);
    p.enqueue(3);
    p.enqueue(2);
    p.enqueue(100);
    p.enqueue(5);

    for(int i = 0; i < 5; i++)
        cout << p.dequeue() << endl;
}