for循环中超过2个条件？

Question

Was wondering if there is a way to compare 3-4 conditions in a for loop? Is there a way to do this with just a for loop or would I need to add an if statement within the loop to control not printing 91 - 96?

I have tried adding an initial condition, brackets around both and around them all but cant seem to get it to print past 90 and pick up at 97.

for (int cntr = 65; cntr >= 65 && cntr < 91 || cntr > 96 && cntr < 122; cntr++)

for (int cntr = 65;  cntr < 91 || cntr > 96 && cntr < 122; cntr++)

Trying to print ASCII char for 65 through 122 without showing 90 through 96. Was trying to get it all in one for loop if possible.

Answer 1

Ok, so fixed it like this:

for (int cntr = 65; cntr < 123; cntr++)
    {
        if(!(cntr >= 91 && cntr <= 96))
        cout << "#" << cntr << " = ASCII Char: " << char(cntr) << endl;
    }

Guess this is the best way to solve the issue for now. Thank You again

Answer 2

As others have pointed out, the central condition is a break condition. As you want it all within one loop you don't want to break when you reach cntr == 91 .

Here's a way to do it neatly in one loop (C++ style):

for (char cntr = 65; cntr < 123; cntr++)
{
    if ( cntr == 91 ) // skips the parts that you don't want
        cntr = 97;

    std::cout << cntr << std::endl;
}

More generally, there are times when you might have multiple genuine break conditions in a loop, but it's best to keep some/most of them out of the first line of the for loop, ie. for ( ... ; ... ; ... ) , as it's unnecessary and often is harder to read. You can just write a break condition at the start of your loop (ie. line 2):

for ( i = 0; break_condition_1; ++i)
{
    if ( break_condition_2 || break_condition_3 )
        break;

    // loop code
}

Answer 3

The answers above/below have explained it quite well about how you can go about having multiple for loop conditions.

But say you are doing something like this (as suggested by Elliott Smith):

for ( i = 0; break_condition_1; ++i)
{
    if ( break_condition_2 || break_condition_3 )
        break;

    // loop code
}

It might be better to simply do this for clarity reasons:

int i = 0;
while (break_condition_1 || break_condition_2 || break_condition_3){
   i++;
}

There is no major difference between for and while loops, aside from the fact for loop is neater to write in certain situations. In your case, I would recommend the while loop.