nested for loops

[dawn]

Hi,

Once again I have a question :

In my app, I have nested loops, very basic stuff, like

for (int i = 0; i < 50; i++)
{
for (int j = 0 ; j < 75; j++)
{
if (expression)
{
do something
}
else
{
do something else
}
}
}

What I would like to do, is when I reach "do something else" move on to the
next step of the outer loop.
So i = 2 ; j = 24
I encounter "do something else"
now I want to move on to i = 3

How can I accomplish this?

Thanks

 

[dawn]

Ok, got that wrong, I actually have 3 nested loops and when I encounter "do
something else" in the innermost loop, I want the outermost loop to move on
to the next step.

Thanks.

 

[Morten Wennevik]

Hm, to step out of one loop you could simply use break, but to step out of
the parent loop too I think you need to set a variable, something like
bool stepOut;

bool stepOut = false;

for (int i = 0; i < 50; i++)
{
for (int j = 0 ; j < 75; j++)
{
for ( int k = 0; k < 100; k++)
{
if (expression)
{
do something
}
else
{
do something else
stepOut = true;
break;
}
}
if(stepOut)
{
stepOut = false;
break;
}
}
}

 

[Tyler Dixon]

Hm, to step out of one loop you could simply use break, but to step out
of the parent loop too I think you need to set a variable, something
like bool stepOut;

bool stepOut = false;

for (int i = 0; i < 50; i++)
{
for (int j = 0 ; j < 75; j++)
{
for ( int k = 0; k < 100; k++)
{
if (expression)
{
do something
}
else
{
do something else
stepOut = true;
break;
}
}
if(stepOut)
{
stepOut = false;
break;
}
}
}

Either that or use a goto. (horrible practice, btw)


outer_loop:
for (int i = 0; i < 50; i++)
{
for (int j = 0 ; j < 75; j++)
{
if (expression)
{
do something
}
else
{
goto outer_loop;
}
}
}

 

[Horatiu Ripa]

There are three cases, I don't know what you really want to do:
1. increment the outer loop, restart immediately the inner loop: use "break"
( from i=4, j=23 you'll have i=5,j=0 and the execution jumps to the
beggining of the inner loop)

2. increment the outer loop, reset the innner loop without restarting the
inner loop: use "i++; j=-1" ( from i=4, j=23 you'll have i=5,j=-1 the inner
loop continues with j=-1!!!; next on inner loop will be i=5; j=0)

3. increment the outer loop whitout restarting/resetting the inner loop:
"i++" ( from i=4, j=23 you'll have i=5,j=23 with continuation of the inner
loop; next on inner loop will be i=5; j=24)

 

[Scarfeet]

The way to do this "by the book", would be to use a while-loop, wouldn't it?
Like:
int i = 0;
int j;
int k;
bool BreakToOuter = false;
while (i<50)
{
j = 0;
while ((j < 75) && !BreakToOuter)
{
k=0;
while ((k < 100) && !BreakToOuter)
{
if (expression)
{
//Do something
}
else
{
//Do something else
BreakToOuter = true;
}
++k;
}
++j;
}
++i;
BreakToOuter = False;
}

No "GOTO"-style behaviour, but you buy that by some more code.

Scarfeet