View Discussion
Improve Article
Save Article
View Discussion
Improve Article
Save Article
The following are different ways to create and initialize a vector in C++ STL
1. Initializing by pushing values one by one :
CPP
#include <iostream>
#include <vector>
using namespace std;
int main()
{
vector<int> vect;
vect.push_back(10);
vect.push_back(20);
vect.push_back(30);
for (int x : vect)
cout << x << " ";
return 0;
}
2. Specifying size and initializing all values :
CPP
#include <iostream>
#include <vector>
using namespace std;
int main()
{
int n = 3;
vector<int> vect(n, 10);
for (int x : vect)
cout << x << " ";
return 0;
}
3. Initializing like arrays :
CPP
#include <iostream>
#include <vector>
using namespace std;
int main()
{
vector<int> vect{ 10, 20, 30 };
for (int x : vect)
cout << x << " ";
return 0;
}
4. Initializing from an array :
CPP
#include <iostream>
#include <vector>
using namespace std;
int main()
{
int arr[] = { 10, 20, 30 };
int n = sizeof(arr) / sizeof(arr[0]);
vector<int> vect(arr, arr + n);
for (int x : vect)
cout << x << " ";
return 0;
}
5. Initializing from another vector :
CPP
#include <iostream>
#include <vector>
using namespace std;
int main()
{
vector<int> vect1{ 10, 20, 30 };
vector<int> vect2(vect1.begin(), vect1.end());
for (int x : vect2)
cout << x << " ";
return 0;
}
6. Initializing all elements with a particular value :
CPP
#include <iostream>
#include <vector>
using namespace std;
int main()
{
vector<int> vect1(10);
int value = 5;
fill(vect1.begin(), vect1.end(), value);
for (int x : vect1)
cout << x << " ";
}
Output
5 5 5 5 5 5 5 5 5 57. Initialize an array with consecutive numbers using std::iota :
C++
#include <iostream>
#include <numeric>
using namespace std;
int main()
{
int arr[5];
iota(arr, arr + 5, 1);
for (int i = 0; i < 5; i++) {
cout << arr[i] << " ";
}
return 0;
}
This article is contributed by Kartik. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to . See your article appearing on the
GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.