C++ Algorithm Function for_each()

C++ Algorithm for_each() function applies the function func to all of the elements in the range from 'first' to 'last'.

Syntax

template <class InputIterator, class Function>
Function for_each (InputIterator first, InputIterator last, Function func);

Parameter

first: It specifies the first element in the list.

last: It specifies the last element in the list.

func: It is an unary function which accepts the argument from the range.

Return value

The function returns 'func'.

Example 1

#include <iostream>
#include <algorithm>
#include <vector>
void newfunction (int k)
{
	std::cout << " " <<k;
}
struct newclass
{
	void operator () (int k)
	{
		std::cout <<" "<<k;
	} 
}
newobject;
int main()
{
	std::vector<int> newvector;
	newvector.push_back(50);
	newvector.push_back(100);
	newvector.push_back(150);
	std::cout << "newvector contains:\n";
	for_each (newvector.begin () , newvector.end (), newfunction);
	std::cout<< "\n newvector contains:\n";
	for_each (newvector.begin (), newvector.end(), newfunction);
	std::cout<<"\n";
	return 0;
}

Output:

newvector contains: 50 100 150
newvector contains: 50 100 150

Example 2

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
void printx1(int b)
{
    cout << b * 2 << " ";
}
struct Class1
{
    void operator() (int b)
    {
        cout << b * 3 << " ";
    }
} obj1;
int main()
{
    int ar[5] = { 6, 7, 8, 9, 10 };
      cout << "Using Arrays:" << endl;
    cout << "Multiple of 2 of elements are : ";
    for_each(ar, ar + 5, printx1);
     cout << endl;
    cout << "Multiple of 3 of elements are : ";
    for_each(ar, ar + 5, obj1);
    cout << endl;
    vector<int> ar1 = { 2,3,5,7,1 };
     cout << "Using Vectors:" << endl;
    cout << "Multiple of 2 of elements are : ";
    for_each(ar1.begin(), ar1.end(), printx1);
    cout << endl;
    cout << "Multiple of 3 of elements are : ";
    for_each(ar1.begin(), ar1.end(), obj1);
    cout << endl;
     }

Output:

Using Arrays:                                                                                                                  
Multiple of 2 of elements are : 12 14 16 18 20                                                                                 
Multiple of 3 of elements are : 18 21 24 27 30                                                                                 
Using Vectors:                                                                                                                 
Multiple of 2 of elements are : 4 6 10 14 2                                                                                    
Multiple of 3 of elements are : 6 9 15 21 3

Complexity

The function moves in a linear way, starting from the first element going towards the last one. For each element of the list value of 'pred' is checked. The search goes on until a mismatch for the ?pred? value is encountered.