Priority Queue in C++

1#include <iostream>
2#include <queue>
3#include <vector>
4using namespace std;
5
6int main() {
7    // Max heap (default - largest element at top)
8    priority_queue<int> pq;
9    
10    pq.push(30);
11    pq.push(10);
12    pq.push(50);
13    pq.push(20);
14    pq.push(40);
15    
16    cout << "Priority Queue (Max Heap):" << endl;
17    cout << "Top element (maximum): " << pq.top() << endl;
18    
19    cout << "\nElements in descending order:" << endl;
20    while (!pq.empty()) {
21        cout << pq.top() << " ";
22        pq.pop();
23    }
24    cout << endl;
25    
26    // Min heap
27    priority_queue<int, vector<int>, greater<int>> minHeap;
28    
29    minHeap.push(30);
30    minHeap.push(10);
31    minHeap.push(50);
32    minHeap.push(20);
33    minHeap.push(40);
34    
35    cout << "\nPriority Queue (Min Heap):" << endl;
36    cout << "Top element (minimum): " << minHeap.top() << endl;
37    
38    cout << "\nElements in ascending order:" << endl;
39    while (!minHeap.empty()) {
40        cout << minHeap.top() << " ";
41        minHeap.pop();
42    }
43    cout << endl;
44    
45    // Custom comparator
46    auto cmp = [](int a, int b) { return a > b; };
47    priority_queue<int, vector<int>, decltype(cmp)> customPQ(cmp);
48    
49    customPQ.push(5);
50    customPQ.push(2);
51    customPQ.push(8);
52    
53    cout << "\nCustom Priority Queue:" << endl;
54    while (!customPQ.empty()) {
55        cout << customPQ.top() << " ";
56        customPQ.pop();
57    }
58    cout << endl;
59    
60    return 0;
61}