How to Initialize a Vector with Default Values in C++?

How to Initialize a Vector with Values between a Range in C++?

Last Updated : 27 Feb, 2024

In C++, vectors are dynamic containers that can resize automatically when elements are inserted or deleted during the runtime. In this article, we will learn how to initialize a vector with a range of values in C++.

Example:

Input: 
start = 1, end =5

Output:
myVector: {1, 5, 3, 4}

Initialize a Vector with Values between a Range in C++

We can initialize a vector with a range of values by using a loop and a random number generator srand() with modular arithmetic such that the number generated would be in between the upper and lower bound.

Approach

Create a random number generator object and use the current time as a seed for a random generator.
Define the start and end of the range for the random numbers.
Use a for loop with n iterations to generate random numbers within the given range and insert them into the vector. To make the number in the desired range, use the formula: start + rand() % (end - start + 1).

C++ Program to Initialize a Vector with Values between a Range

C++

// C++ Program to show how to Initialize a Vector with
// Values between a Range
#include <cstdlib>
#include <ctime>
#include <iostream>
#include <vector>
using namespace std;

int main()
{
    // Use current time as seed for random generator
    srand(time(0));

    // Start and end of range
    int start = 1, end = 5;

    // Vector declaration
    vector<int> myVector;

    // Initializing the vector with a range of random values
    for (int i = start; i <= end; i++) {
        int randNum = start + rand() % (end - start + 1);
        myVector.push_back(randNum);
    }

    // Printing the vector
    cout << "Vector: ";
    for (int i : myVector) {
        cout << i << " ";
    }
    cout << endl;

    return 0;
}

Output

Vector: 2 5 1 4 3

Time Complexity: O(N) where N is the number of elements.
Auxiliary Space: O(N)

How to Initialize a Vector with Default Values in C++?

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