std::generate_n in C++ (original) (raw)

Last Updated : 23 Jul, 2025

std::generate is an STL algorithm, which is used to generate numbers based upon a generator function, and then, it assigns those values to the elements in the container in the range [first, last). The generator function has to be defined by the user, and it is called successively for assigning the numbers. Now, there can be a scenario, where we want to assign values only to the first n elements, for that we have another STL algorithm std::generate_n, which has the following syntax:Template function:

OutputIterator generate_n (OutputIterator first, Size n, Generator gen);

first: Output iterator pointing to the beginning of the container. n: No. of elements to be assigned a value, using generator function. gen: A generator function for generating the values.

Returns: It doesnot have a void return type like std::generate, but, in fact, it returns an iterator pointing to the element that follows the last element whose value has been generated.

CPP `

// C++ program to demonstrate the use of std::generate_n #include #include #include

// Defining the generator function int gen() { static int i = 0; return ++i; }

using namespace std; int main() { int i;

// Declaring a vector of size 10
vector<int> v1(10);

// using std::generate_n
std::generate_n(v1.begin(), 10, gen);

vector<int>::iterator i1;
for (i1 = v1.begin(); i1 != v1.end(); ++i1) {
    cout << *i1 << " ";
}
return 0;

}

`

Output:

1 2 3 4 5 6 7 8 9 10