Vectors in C++

In C++, vectors are used to store elements of similar data types. However, unlike arrays, the size of a vector can grow dynamically.

Vectors are part of the C++ Standard Template Library. To use vectors, we need to include the vector header file in our program.

Declaraton

vector<int> v; //Declare an empty vector of int type
vector<int> vector1 = {1, 2, 3, 4, 5}; //Initialize with 1,2,3,4,5
vector<int> vector2 {1, 2, 3, 4, 5}; //Initialize with 1,2,3,4,5
vector<int> vector3(5, 12); //⭐ Initialize with 12,12,12,12,12
vector<int, vector<int>> vector2D(5, vector<int>(10,0)) //Initialize a 5x10 Vector with 0s 

Adding elements to vector

vector<int> num {1, 2, 3, 4, 5};
num.push_back(6);

Note: We can also use the insert() and emplace() functions to add elements to a vector.

Accessing Elements

vector<int> num {1, 2, 3, 4, 5};
cout << "Element at Index 0: " << num.at(0) << endl;

Note: Like an array, we can also use the square brackets [] to access vector elements. For example,

vector<int> num {1, 2, 3};
cout << num[1];  // Output: 2

However, the at() function is preferred over [] because at() throws an exception whenever the vector is out of bound, while [] gives a garbage value

Changing Elements

num.at(1) = 9;

Deleting Last Element

v.pop_back()