div() function in C++

Given a numerator and denominator, we have to find their quotient and remainder without using the modulo or division operator. div() function allows us to do the same task easily and efficiently.

div() function : Returns the integral quotient and remainder of the division of number by denom ( number/denom ) as a structure of type div_t, ldiv_t or lldiv_t, which has two members: quot and rem. 

Syntax: 

div_t div(int numerator, int denominator);
ldiv_t div(long numerator, long denominator);
lldiv_t div(long long numerator, long long denominator);

When we use div() function, it returns a structure that contains the quotient and remainder of the parameters. The first parameter passed in a div() function is taken as numerator and the 2nd parameter is taken as the denominator. 

For int values, the structure returned is div_t. This structure looks like this: 

Time Complexity: O(1)

Space Complexity: O(1)

C++

// CPP program to illustrate
// div() function
#include <iostream>
#include <cstdlib>
using namespace std;

int main()
{
    div_t result1 = div(100, 6);

    cout << "Quotient of 100/6 = " <<
                      result1.quot << endl;
    cout << "Remainder of 100/6 = " <<
                       result1.rem << endl;

    ldiv_t result2 = div(19237012L,251L);

    cout << "Quotient of 19237012L/251L = " <<
                          result2.quot << endl;
    cout << "Remainder of 19237012L/251L = " <<
                            result2.rem << endl;

    return 0;
}

Similarly, for long values, structure ldiv_t is returned and for long long values, structure lldiv_t is returned.

Where is it useful ?

The question is, since we have both % and / operators, why should we use div() function?. Well, in a program where we require both – quotient and remainder, using div() function would be the best choice as it calculates both the values for you at once, moreover, it requires less time as compared to using % and / functions one by one. 
While using div() function, both %operator and using div() will return the same value of remainder, i.e if we’re getting negative value of remainder by using %operator then we will get negative value of remainder using div() function too. Eg, div(-40,3) will give remainder of ‘-1’. . So, div() function can be efficiently used according to one’s requirement. 

What happens when the denominator is 0?

If any one of the part of this function, i.e. the remainder or the quotient cannot be represented or cannot find a result, then the whole structure shows an undefined behavior. 

NOTE: While using div() function, remember to include cstdlib.h library in your program. 

Examples: 

Input : div(40, 5)
Output :quot = 8 rem = 0

Input :div(53, 8)
Output :quot = 6 rem = 5

Input : div(-40,3)
Output : quot = -13 , rem = -1

Implementation:

C++

// CPP program to illustrate
// div() function
#include <iostream>
#include <cstdlib>
using namespace std;

int main()
{
    div_t result1 = div(100, 6);

    cout << "Quotient of 100/6 = " <<
                      result1.quot << endl;
    cout << "Remainder of 100/6 = " <<
                       result1.rem << endl;

    ldiv_t result2 = div(19237012L,251L);

    cout << "Quotient of 19237012L/251L = " <<
                          result2.quot << endl;
    cout << "Remainder of 19237012L/251L = " <<
                            result2.rem << endl;

    return 0;
}

Output: 

Quotient of 100/6 = 16
Remainder of 100/6 = 4
Quotient of 19237012L/251L = 76641
Remainder of 19237012L/251L = 121