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Difference between std::vector and std::array in C++
The following are the differences between vector and array −
- Vector is a sequential container to store elements and not index based.
- Array stores a fixed-size sequential collection of elements of the same type and it is index based.
- Vector is dynamic in nature so, size increases with insertion of elements.
- As array is fixed size, once initialized can’t be resized.
- Vector occupies more memory.
- Array is memory efficient data structure.
- Vector takes more time in accessing elements.
- Array access elements in constant time irrespective of their location as elements are arranged in a contiguous memory allocation.
Vectors and arrays can be declared with the following syntax −
Vector declaration:vector<datatype>array name;
Array declaration:type array_name[array_size];
Vector initialization:vector<datatype>array name={values};
Array initialization:datatype arrayname[arraysize] = {values};std::vector:
Example Code
#include <iostream>
#include <vector>
using namespace std;
int main() {
vector<vector<int>>v{ { 4, 5, 3 }, { 2, 7, 6 }, { 3, 2, 1 ,10 } };
cout<<"the 2D vector is:"<<endl;
for (int i = 0; i < v.size(); i++) {
for (int j = 0; j < v[i].size(); j++)
cout << v[i][j] << " ";
cout << endl;
}
return 0;
}Output
the 2D vector is: 4 5 3 2 7 6 3 2 1 10
std:: array:
Example Code
#include<iostream>
#include<array>
using namespace std;
int main() {
array<int,4>a = {10, 20, 30, 40};
cout << "The size of array is : ";
//size of the array using size()
cout << a.size() << endl;
//maximum no of elements of the array
cout << "Maximum number of elements array can hold is : ";
cout << a.max_size() << endl;
// Printing array elements using at()
cout << "The array elements are (using at()) : ";
for ( int i=0; i<4; i++)
cout << a.at(i) << " ";
cout << endl;
// Filling array with 1
a.fill(1);
// Displaying array after filling
cout << "Array after filling operation is : ";
for ( int i=0; i<4; i++)
cout << a[i] << " ";
return 0;
}Output
The size of array is : 4 Maximum number of elements array can hold is : 4 The array elements are (using at()) : 10 20 30 40 Array after filling operation is : 1 1 1 1
Updated on: 30-Jul-2019
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