The **`find_if()` function** is available in the `<algorithm.h>` header file in C++. This function helps search for an element in a list based on a condition. The condition needs to be `true` for the element to be searched. 

# Parameters
The `find_if()` function accepts the following parameters:

* **`first`:** This is an iterator that points to the first index of the array or vector where we want to perform the search operation.

* **`last`:** This is an iterator that points to the last index of the array or vector to where we want to perform the search operation.

* **`condition`:** This is a unary function that accepts one element and returns a boolean value indicating whether the condition is satisfied or not.

# Return 
The `find_if()` function returns an iterator pointing to the first element satisfying the condition. If no such element is found, it returns an iterator pointing to the `last` element of the vector.

# Code
Let's have a look at the code:

#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

bool IsOdd (int i) {
  return (i % 2) == 1;
}

int main () {
  vector<int> vec = {10, 25, 5, 30, 3};
  auto it = find_if(vec.begin(), vec.end(), IsOdd);
  
  cout << "The first odd value is " << *it;

  return 0;
}

## Explanation:
* From _lines 1 to 3_, we import the required header files.
* In _line 6_, we create a unary function that returns a boolean value indicating whether the number is #key# odd: return true #key# or #key# not: return false #key#. 
* In _line 11_, we create a vector of integers.
* In _line 12_, we call the `find_if()` function and pass all the required parameters.
* In _line 14_, we print the first element that satisfies the given #key# condition: the number is odd #key#.

How to use the find_if() function in C++

find_if() in C++ searches a range based on a condition, returning an iterator to the first match.