Deque (Double-ended Queue) in C++

1#include <iostream>
2#include <deque>
3using namespace std;
4
5int main() {
6    // Create deque
7    deque<int> dq;
8    
9    // Add elements at both ends
10    dq.push_back(10);
11    dq.push_back(20);
12    dq.push_back(30);
13    dq.push_front(5);
14    dq.push_front(1);
15    
16    cout << "Deque elements: ";
17    for (int num : dq) {
18        cout << num << " ";
19    }
20    cout << endl;
21    
22    cout << "Front: " << dq.front() << endl;
23    cout << "Back: " << dq.back() << endl;
24    cout << "Size: " << dq.size() << endl;
25    
26    // Access elements by index
27    cout << "Element at index 2: " << dq[2] << endl;
28    cout << "Element at index 2 (at): " << dq.at(2) << endl;
29    
30    // Remove from front
31    dq.pop_front();
32    cout << "\nAfter pop_front: ";
33    for (int num : dq) {
34        cout << num << " ";
35    }
36    cout << endl;
37    
38    // Remove from back
39    dq.pop_back();
40    cout << "After pop_back: ";
41    for (int num : dq) {
42        cout << num << " ";
43    }
44    cout << endl;
45    
46    // Insert at specific position
47    dq.insert(dq.begin() + 1, 15);
48    cout << "\nAfter inserting 15 at index 1: ";
49    for (int num : dq) {
50        cout << num << " ";
51    }
52    cout << endl;
53    
54    // Erase element
55    dq.erase(dq.begin() + 1);
56    cout << "After erasing element at index 1: ";
57    for (int num : dq) {
58        cout << num << " ";
59    }
60    cout << endl;
61    
62    return 0;
63}