Sequence Containers

Overview

Sequence containers store data in a linear manner. `vector` is a dynamic array (the default choice). `list` is a doubly-linked list. `deque` is a double-ended queue.

Syntax

cpp

#include <vector>
#include <list>
#include <deque>

// Vector (Dynamic Array - O(1) back insertion, O(N) front)
std::vector<int> v;
v.push_back(10);
v[0]; // Fast random access

// List (Doubly Linked List - O(1) insertion anywhere, no random access)
std::list<int> l;
l.push_back(10); l.push_front(5);

// Deque (Double Ended Queue - O(1) front/back insertion, fast access)
std::deque<int> dq;
dq.push_back(10); dq.push_front(5);

Common Pitfalls

Using `push_front` on a `vector`. It takes O(N) time because every single element must be shifted right. Use `deque` instead.

Interview Tips

When to use what: Use `vector` 95% of the time. Use `list` if you have massive amounts of insertions/deletions in the MIDDLE of the sequence. Use `deque` if you need to push/pop at BOTH the front and back.

Real-World Example

Using vector for a dynamic inventory system.

example

cpp

#include <iostream>
#include <vector>
using namespace std;

int main() {
    vector<string> inventory;
    
    // Add items
    inventory.push_back("Sword");
    inventory.push_back("Shield");
    inventory.push_back("Potion");
    
    // Remove last item
    inventory.pop_back();
    
    cout << "Inventory size: " << inventory.size() << endl;
    return 0;
}

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