# Find elements of an array which are divisible by N using STL in C++

Given with an array and the task is to find the number which are divisible by N using standard template library in C++.

To solve this problem we are using the function count_if() present in C++ standard template library.

What is a count_if() function?

## Syntax

count_if(LowerBound, UpperBound, function)

Description − This function returns the number of elements in an array that satisfies the given condition. It takes three parameters.

• Lower Bound − It points to the first element of an array or any other sequence.
• Upper Bound − It points to the last element of an array or any other sequence.
• Function − It returns the Boolean value on the basis of the condition specified.

## Example

Input-: array[] = {2, 4, 1, 5, 8, 9}
N = 4
Output-: Elements divisible by 4: 2
Input-: array[] = {1, 2, 3, 4, 5, 10}
N = 2
Output: Elements divisible by 2: 3

Approach used in the below program is as follows

• Input the integer values in an array of integer type.
• Create the bool function to check whether the element of an array is divisible by the user input value N.
• Call the function count_if() which takes the first and the last element and the function as the parameter.

## Live Demo

#include <bits/stdc++.h>
using namespace std;
int n;
//function to check if the element is divisible by n
bool check(int i) {
if (i % n == 0)
return true;
else
return false;
}
int main() {
int arr[] = {2, 4, 1, 5, 8, 9};
n = 4;
int size = sizeof(arr) / sizeof(arr[0]);
int temp = count_if(arr, arr + size, check);
cout<<"Elements divisible by "<<n<< ": " <<temp;
return 0;
}

## Output

If we run the above code it will generate the following output −

Elements divisible by 4: 2