if (flag)

[PK Dey]

Write your question here.

    for (i = 0; i < m; ++i) 
    {
        flag = 1;
        for (j = 0; j < n; ++j) 
        {
            if (a2[i] == a1[j]) 
            {
                flag = 0;
                break;
            }
        }
        if (flag) {
            u[k] = a2[i];
            k++;
        }
    }

What kind of condition is this in the following line? Could someone please explain?

if (flag)

[dutch]

Write your answer here.

What do you mean "what kind of condition is this"?

[Handy Andy]

Hello PK Dey,

The first thing to understand is whether it is an if condition, a for condition or the condition of a do/while or while loop they all evaluate to a bool type result.

So it does not matter how "flag" is defined. either a "bool" or an "int" it still ends up as a bool meaning that (0) zero is false and (1) is true. Any result that is not (0) zero is considered true and changed to a 1.

To look at it another way if (flag) is a shorthand for if (flag == 1) and for if (flag == 0) you would use
if (!flag).

Just like i++ is short for i = i +1 it is a way to better use what the language offers.

Andy

[PK Dey]

To look at it another way if (flag) is a shorthand for if (flag == 1) and for if (flag == 0) you would use
if (!flag).

Lot of Thanks Handy Andy!

[Handy Andy]

Any time.

[seeplus]

if (flag) is shorthand for (flag != 0)
if (!flag) is shorthand for (flag == 0)

[JLBorges]

C++: if(flag) is equivalent to if( bool(flag) ) ie. flag is contextually converted to bool
https://en.cppreference.com/w/cpp/language/implicit_conversion#Contextual_conversions

C: if(flag) is equivalent to if( flag != 0 ) ie. flag is compared with integer zero
https://en.cppreference.com/w/c/language/if

[jonnin]

the reverse it true as well, boolean expressions result in integer 0 or 1 for false or true. This can be very handy.