std::find_if , std::find_if_not in C++

Difficulty Level : Easy
Last Updated : 26 Jul, 2017

std :: find_if

Returns an iterator to the first element in the range [first, last] for which pred(Unary Function) returns true. If no such element is found, the function returns last.
Function Template :

InputIterator find_if (InputIterator first, InputIterator last, UnaryPredicate pred);

first, last :range which contains all the elements between first
and last, including the element pointed by first but
not the element pointed by last.

pred : Unary function that accepts an element in the range
as argument and returns a value in boolean.

Return value :
Returns an iterator to the first element in the range
[first, last] for which pred(function) returns true. If
no such element is found, the function returns last.

std :: find_if_not

Returns an iterator to the first element in the range [first, last] for which pred(Unary Function) returns false. If no such element is found, the function returns last.
Function Template :

InputIterator find_if_not (InputIterator first, InputIterator last, UnaryPredicate pred);

Return value :
Returns an iterator to the first element in the range
[first, last] for which pred(function) returns false.

// CPP program to illustrate
// std::find_if and std::find_if_not
#include <bits/stdc++.h>
  
// Returns true if argument is odd
bool IsOdd(int i)
{
    return i % 2;
}
  
// Driver code
int main()
{
    std::vector<int> vec{ 10, 25, 40, 55 };
  
    // Iterator to store the position of element found
    std::vector<int>::iterator it;
  
    // std::find_if
    it = std::find_if(vec.begin(), vec.end(), IsOdd);
    std::cout << "The first odd value is " << *it << '\n';
  
        // Iterator to store the position of element found
        std::vector<int>::iterator ite;
  
    // std::find_if_not
    ite = std::find_if_not(vec.begin(), vec.end(), IsOdd);
  
    std::cout << "The first non-odd(or even) value is " << *ite << '\n';
  
        return 0;
}

Output:

The first odd value is 25
The first non-odd(or even) value is 10

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