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Vectors

Vector Type

During the creation of a C++ vector, the data type of its elements must be specified. Once the vector is created, the type cannot be changed.

Index

An index refers to an element’s position within an ordered list, like a vector or an array. The first element has an index of 0.

A specific element in a vector or an array can be accessed using its index, like name[index].

std::vector<double> order = {3.99, 12.99, 2.49}; // What's the first element? std::cout << order[0]; // What's the last element? std::cout << order[2];

.size() Function

The .size() function can be used to return the number of elements in a vector, like name.size().

std::vector<std::string> employees; employees.push_back("michael"); employees.push_back("jim"); employees.push_back("pam"); employees.push_back("dwight"); std::cout << employees.size(); // Prints: 4

Vectors

In C++, a vector is a dynamic list of items, that can shrink and grow in size. It is created using std::vector<type> name; and it can only store values of the same type.

To use vectors, it is necessary to #include the vector library.

#include <iostream> #include <vector> int main() { std::vector<int> grades(3); grades[0] = 90; grades[1] = 86; grades[2] = 98; }

.push_back() & .pop_back()

The following functions can be used to add and remove an element in a vector:

  • .push_back() to add an element to the “end” of a vector
  • .pop_back() to remove an element from the “end” of a vector
std::vector<std::string> wishlist; wishlist.push_back("Oculus"); wishlist.push_back("Telecaster"); wishlist.pop_back(); std::cout << wishlist.size(); // Prints: 1