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vector:: assign() is an STL in C++ which assigns new values to the vector elements by replacing old ones. It can also modify the size of the vector if necessary.
The syntax for assigning constant values:
vectorname.assign(int size, int value)Parameters: size - number of values to be assignedvalue - value to be assigned to the vectorname
Program 1: The program below shows how to assign constant values to a vector
CPP
// CPP program to demonstrate
// how to assign constant values to a vector
#include <bits/stdc++.h>
using namespace std;
int main()
{
vector<int> v;
v.assign(7, 100);
cout << "Size of first: "
<< int(v.size()) << '\n';
cout << "Elements are\n";
for (int i = 0; i < v.size(); i++)
cout << v[i] << endl;
return 0;
}
Output
Size of first: 7Elements are100100100100100100100
The syntax for assigning values from an array or list:
vectorname.assign(arr, arr + size)Parameters: arr - the array which is to be assigned to a vectorsize - number of elements from the beginning which has to be assigned.
Program 2: The program below shows how to assign values from an array or list
CPP
// CPP program to demonstrate
// how to assign values to a vector
// from a list
#include <bits/stdc++.h>
using namespace std;
int main()
{
vector<int> v1;
int a[] = { 1, 2, 3 };
// assign first 2 values
v1.assign(a, a + 2);
cout << "Elements of vector1 are\n";
for (int i = 0; i < v1.size(); i++)
cout << v1[i] << " ";
vector<int> v2;
// assign first 3 values
v2.assign(a, a + 3);
cout << "\nElements of vector2 are\n";
for (int i = 0; i < v2.size(); i++)
cout << v2[i] << " ";
return 0;
}
Output
Elements of vector1 are1 2 Elements of vector2 are1 2 3
The syntax for modifying values from a vector
vectorname.assign(InputIterator first, InputIterator last) Parameters: first - Input iterator to the initial position range.last - Input iterator to the final position range.
Program 3: The program below shows how to modify the vector
CPP
// CPP program to demonstrate
// how to modify vector size
#include <bits/stdc++.h>
using namespace std;
int main()
{
vector<int> v;
v.assign(7, 100);
cout << "Size of first: " << int(v.size()) << '\n';
cout << "Elements are\n";
for (int i = 0; i < v.size(); i++)
cout << v[i] << endl;
// modify the elements
v.assign(v.begin(), v.begin() + 3);
cout << "\nModified VectorElements are\n";
for (int i = 0; i < v.size(); i++)
cout << v[i] << endl;
return 0;
}
Output
Size of first: 7Elements are100100100100100100100Modified VectorElements are100100100
Time Complexity – Linear O(N)
Syntax for assigning values with initializer list:
vectorname.assign((initializer_list)Parameter: initializer_list
Program 4:The program below shows how to assign a vector with an initializer list.
C++
#include <iostream>
#include <vector>
using namespace std;
int main()
{
vector<int> v;
// Initialize v with an initialization list
v.assign({ 1, 2, 3 });
cout << "The list is:" << endl;
for (auto i = v.begin(); i != v.end(); i++)
{
// Printing 1 2 3 as output
cout << *i << " ";
}
return 0;
}
Output
The list is:1 2 3
Last Updated : 09 Jun, 2022
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