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How to initialize a vector in C++?
Initialization vector can be done in many ways
1) Initialize a vector by push_back() method
Algorithm
Begin Declare v of vector type. Call push_back() function to insert values into vector v. Print “Vector elements:”. for (int a : v) print all the elements of variable a. End.
Example
#include<iostream>
#include <bits/stdc++.h>
using namespace std;
int main() {
vector<int> v;
v.push_back(6);
v.push_back(7);
v.push_back(10);
v.push_back(12);
cout<<"Vector elements:"<<endl;
for (int a : v)
cout << a << " ";
return 0;
}Output
Vector elements: 6 7 10 12
2) Initialize a vector by array
Algorithm
Begin Create a vector v. Initialize vector like array. Print the elements. End.
Example
#include <bits/stdc++.h>
using namespace std;
int main() {
vector<int> v{ 1, 2, 3, 4, 5, 6, 7 };
cout<<"vector elements:"<<endl;
for (int a : v)
cout << a << " ";
return 0;
}Output
vector elements: 1 2 3 4 5 6 7
3) Initialize a vector from another vector
Algorithm
Begin Create a vector v1. Initialize vector v1 by array. Initialize vector v2 by v1. Print the elements. End.
Example
#include<iostream>
#include <bits/stdc++.h>
using namespace std;
int main() {
vector<int> v1{ 1, 2, 3, 4, 5, 6, 7 };
vector<int> v2(v1.begin(), v1.end());
cout<<"vector elements:"<<endl;
for (int a : v2)
cout << a << " ";
return 0;
}Output
vector elements: 1 2 3 4 5 6 7
4) Initialize a vector by specifying size and elements
Algorithm
Begin Initialize a variable s. Create a vector v with size s and all values with 7. Initialize vector v1 by array. Initialize vector v2 by v1. Print the elements. End.
Example
#include<iostream>
#include <bits/stdc++.h>
using namespace std;
int main() {
int s= 5;
vector<int> v(s, 7);
cout<<"vector elements:"<<endl;
for (int a : v)
cout << a << " ";
return 0;
}Output
vector elements: 7 7 7 7 7
Updated on: 30-Jul-2019
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