Following are different ways to create and initialize a vector in C++ STL
Initializing by pushing values one by one :
// CPP program to create an empty vector // and push values one by one. #include <bits/stdc++.h> using namespace std; int main() { // Create an empty vector vector<int> vect; vect.push_back(10); vect.push_back(20); vect.push_back(30); for (int x : vect) cout << x << " "; return 0; } |
Output:
10 20 30
Specifying size and initializing all values :
// CPP program to create an empty vector // and push values one by one. #include <bits/stdc++.h> using namespace std; int main() { int n = 3; // Create a vector of size n with // all values as 10. vector<int> vect(n, 10); for (int x : vect) cout << x << " "; return 0; } |
Output:
10 10 10
Initializing like arrays :
// CPP program to initialize a vector like // an array. #include <bits/stdc++.h> using namespace std; int main() { vector<int> vect{ 10, 20, 30 }; for (int x : vect) cout << x << " "; return 0; } |
Output:
10 20 30
Initializing from an array :
// CPP program to initialize a vector from // an array. #include <bits/stdc++.h> 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; } |
Output:
10 20 30
Initializing from another vector :
// CPP program to initialize a vector from // another vector. #include <bits/stdc++.h> 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; } |
Output:
10 20 30
Initializing all elements with a particular value :
#include <bits/stdc++.h> 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 5
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