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# Find elements of an Array which are Odd and Even using STL in C++

Given with an array and the task is to find the number of odd and even elements in an array 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} Output-: Odd elements are: 1, 5 and 9. So, total number of odds is 3 Even elements are: 2, 4 and 8 Input-: array[] = {1, 2, 3, 4, 5, 10} Output-: Odd elements are: 1, 3 and 5. So, total number of odds is 3 Even elements are: 2, 4 and 10. So, total number of evens is 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 odd or not. If the selected elements are odd than the remaining elements will be even.
- Call the function count_if() which takes the first and the last element and the function as the parameter.

## Example

#include <bits/stdc++.h> using namespace std; // Function to check if the element is odd or even bool check(int i) { if (i % 2 != 0) return true; else return false; } int main() { int arr[] = { 2, 10, 1, 3, 7, 4, 9 }; int size = sizeof(arr) / sizeof(arr[0]); int temp = count_if(arr, arr + size, check); cout << "Odds are : " <<temp << endl; cout << "Evens are : " << (size - temp) << endl; return 0; }

## Output

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

Odds are: 4 Evens are: 3

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