How to generate a vector with random values in C++?

Generating a vector with random values means creating a vector of n elements and initialize each element some random values. In this article, we will learn different methods to initialize a vector with random values in C++.

The recommended method to initialize a vector with random values is by using a random number generator from C++'s <random> library. Let's take a look at an example:

#include <bits/stdc++.h>
using namespace std;

int main() {
  vector<int> v(10);

    // Create a random number generator between 0 to 100
    random_device rd;
    mt19937 gen(rd());
    uniform_int_distribution<> dis(0, 100);

    // Initialize vector elements with random values
    for (int i = 0; i < 10; ++i)
        v[i] = dis(gen);

    for (auto i : v)
        cout << i << " ";
    return 0;
}

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Explanation: The <random> library allows you to generate numbers in a specific range using distribution objects like uniform_int_distribution.

C++ also provides some other methods to generate a vector with random values. Some of them are as follows:

Using rand() Function

The rand() function generates pseudo-random numbers which can be used to populate a vector by calling rand() for each element and storing the results.

#include <bits/stdc++.h>
using namespace std;

int main() {
    vector<int> v(10);

    // Generate 10 random numbers between 0 and 100
    for (int i = 0; i < 10; ++i)
        v[i] = rand() % 100;

    for (auto i : v)
        cout << i << " ";
    return 0;
}

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Explanation: The rand() function generates pseudo-random integers. The modulo operator (%) is used to limit the range of random values.

Using generate() with Random Function

The generate() function from <algorithm> allows you to populate a vector with given values. You can use the random number generator to provide the random values for generate() function.

#include <bits/stdc++.h>
using namespace std;

int main() {
    vector<int> v(10);

    // Populate the vector with random values
    generate(v.begin(), v.end(), []() {
      	return rand() % 100;
    });

    for (auto i : v)
        cout << i << " ";
    return 0;
}

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Using fill_n() with Random Values

The fill_n() function can also be used in combination with a random number generator in a similar way as generate() function.

#include <bits/stdc++.h>
using namespace std;

int main() {
    vector<int> v;

    // Fill vector with 10 random values
    fill_n(back_inserter(v), 10, rand() % 100);

    for (auto i : v)
        cout << i << " ";
    return 0;
}

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