std::generate_n in C++
Last Updated :
21 Jul, 2017
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.
#include <iostream>
#include <vector>
#include <algorithm>
int gen()
{
static int i = 0;
return ++i;
}
using namespace std;
int main()
{
int i;
vector< int > v1(10);
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
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