Get the longest sequence in hailstone program

[iikitty]

The following is a part of a hailstone cpp program.
I want to write an option to let users enter 2 numbers and the program evaluates the longest sequence the number has within the 2-number range and return the count.
I have been struggling it for hours :P but the program is not working I don't know why, may I ask whats wrong with it?

Thanks for any help in advance.

int longestHailstoneSequenceLength(int start, int end)
{
    int max = 0;
    int s= start;
    while (s!=1)
    {
        int count = 0;
        for (int s; s<(end+1); s++)
        {
            int i= count;
            for (i = 2; i<1000; i++)
            {
        if (s%2==0)
            {
                s=s/2;
            }else
            {
                s=(3*s)+1;
            }
            if (s==1) break;
            if (max<count)
            {
                max=count;
            }
            }
        }
    }
    return max;
}

[2kaud]

int s= start;
while (s!=1)
...
for (int s; s<(end+1); s++)

The s used within the for loop is a different s to that used in the outer while loop. The s in the while loop is set to start and is never changed! The s used in the for loop is not initialised so starts with some random value.

[iikitty]

i changed the for loop like this:

		for (s=start; s<(end+1); s++)
		{
            int i= count;
            for (i = 2; i<1000; i++)
            {

however its still not working (, i initialised the s to be same as start, and start with a loop counting sequence for one number first and the outer for loop goes from "start" till the "end" number, and change the max as count whenever it meets a number larger than max, and finally return the max
is the logic alright or did i miss any steps its not working?

[2kaud]

is the logic alright or did i miss any steps its not working?

Your logic isn't right. Have you tried stepping through the code using the debugger to see where it departs from what expected? Is this a homework assignment?

If you just want the max number of the hailstone sequences, the function only needs about 6 lines of code.

[iikitty]

i tried printing out the numbers when its running and found it keep repeating printing "1" out nonstop I have to stop it manually...Im not sure which part went wrong but Im sure it never run the number after "start" number :/
i modified a bit for s but still not working:

    int s= start;
    while (s!=1)
    {
		int count = 0;
		for (s=start; s<(end+1); s++)
		{
            int i= count;
            for (i = 2; i<1000; i++)
            {

I am a beginner in programming n shame Im still not that familiar xp
Yes I want the max only, so should I use a sequence to store or how should I modify?
I want to understand the concept behind xp

[2kaud]

Try this

int longestHailstoneSequenceLength(int start, int end)
{
int max = 1;

	for (int s = start; s <= end; s++)
		for (int count = 1, ss = s; ss > 1; ss = (ss % 2) ? (3 * ss) + 1 : ss / 2, max = (++count > max) ? count : max);

	return max;
}

If you don't follow the code then see
http://www.learncpp.com/cpp-tutorial...-if-operators/

which explains use of the , ? and :

[iikitty]

it worksss couldn't imagine code could be that short :P still have a lot to learn
cuz Im using Xcode the first few times i didn't know where I can sort out my bug is except the formatting xp

[iikitty]

so...the increment in the for loop is count ++, and in terms of if-else is it like:

        for (int count=2, ss=s;ss>1;count++)
        {
            if (ss%2==0)
            {
                ss=ss/2;
            }else
            {
                ss=3*ss+1;
            }
            if (max<count)
            {
                max=count;
            }
        }
        return max;

Thanks so much

[OReubens]

        for (int count=2, ss=s;ss>1;count++)

Get into the habbit of writing PREincrements (++count) rather than post increments (count++).

The only time you want a post-increment is when you want the exact behaviour the post increment gives you. If you don't know/understand the difference (yet), then use pre-increments.

the same is true for decrements, use --count, unless you specifically want the behaviour of count--.

No I'm not going to explain. Just get into the habbit of doing this. It'll make your life a lot easier learning to do this NOW, rather than weening you off the post-inc/decrement later on.