Why this answer is 12? Can help me to explain it?

Question

int sum (int i) {return ++i;}
int main ()
{
for(int = 0; i <=1; i++)
{cout<<sum(i);
}

Answer 1

The answer isn't twelve really, but rather the for loop first outputs 1 and then outputs 2, and they are placed next to each other because there is no return ("\n" or endl) in the cout.

Answer 2

1st cycle: the return value is 1 (first i value is incremented then returned)
2nd cycle: like the first cycle 1 incremented to 2 and then returned to caller.

Answer 3

Yeah dear, you are right.
Delete that.

Answer 4

If you were to change the for loop so that the conditional were i <= 2 instead, then the output would be 123. If you added << endl to the end of the cout so that it reads:
cout << sum(i) << endl;
the output will be
1
2
3
outputing the numbers all on different lines instead of next to each other on the same line.

Answer 5

@Babak no that will change the output entirely, because you are now incrementing the i in the for loop twice.

Answer 6

lul

Answer 7

so if the code never use return on the main function, it will has 12 for the answer?

Answer 8

thanks for the answer..finally i got it