help with java code for project euler

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This is my code for project euler #9. it is meant to find the pythagorean triplet for which a+b+c=1000 and then print the product of a*b*c. however my code just runs forever with no answer being printed. any help would be appreciated.

Java

public class Problem8 {

	public static void main(String[] args) {
		
		for(int a=1, b=1;;)
		{ double c= Math.sqrt((a*a) + (b*b));
		
		if ((a+b+c) == 1000){
			System.out.println(a*b*c);
			return;}
		a++;
		c= Math.sqrt((a*a) + (b*b));
		if ((a+b+c) == 1000){
			System.out.println(a*b*c);
			return;}
		b++;
		c= Math.sqrt((a*a) + (b*b));
		if ((a+b+c) == 1000){
			System.out.println(a*b*c);
			return;}
		
		}
		

	}

}

Posted 24-Jul-15 6:07am

Member 11861229

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Richard Deeming · Answer 1 · 2015-07-24T06:56:00

This is due to the way you're incrementing the variables - a and b will always be either the same number, or consecutive numbers.

plain

First iteration: (1, 1); (2, 1); (2, 2);
Second iteration: (2, 2); (3, 2); (3, 3);
...

Since the Pythagorean triplet which sums to 1000 doesn't involve consecutive numbers, your code will never find the answer. Since you haven't specified an upper bound for the loop, it will keep running forever.

Try a nested loop, and specify sensible upper-bounds. For example:

C#

for (int a = 1; a < 1000; a++)
{
    for (int b = a; b < 1000; b++)
    {
        ...
    }
}

Sergey Alexandrovich Kryukov · Answer 2 · 2015-07-24T06:24:00

Solution 1

If you explicitly write some "infinite" loop, it will be executed "infinitely".

Your loop just assigns 1 to a and b and repeats unconditionally, because there is no condition. :-) So what else could you expect? Please see:
https://docs.oracle.com/javase/tutorial/java/nutsandbolts/for.html[^].

—SA

Posted 24-Jul-15 6:24am

Sergey Alexandrovich Kryukov

Updated 24-Jul-15 6:25am

v2

Comments

Member 11861229 24-Jul-15 12:27pm

But the if statements are supposed to print an answer and then end the code with the return statement

Sergey Alexandrovich Kryukov 24-Jul-15 12:29pm

Sorry, it's enough.
—SA

Member 11861229 24-Jul-15 12:32pm

so why does it run continuously without an answer

Sergey Alexandrovich Kryukov 24-Jul-15 12:35pm

Please stop it. The answer to your second question is more than obvious.

If you want to go in for programming, learn programming. In this case, execute your code under the debugger and see what's going on, maybe it can help you. But it's apparent to an unarmed eye. I answered to your original question, so please first accept the answer formally.

—SA

Richard MacCutchan · Answer 3 · 2015-07-24T07:16:00

Solution 3

You know that the pythagorean triplet follows the rule 3-4-5, so start with those numbers. Repeat your loops by incrementing the values which ensure that each side remains an integer. When they sum to 1000 or greater you stop.

Posted 24-Jul-15 7:16am

Richard MacCutchan

Patrice T · Answer 4 · 2015-07-24T08:08:00

Obviously you don't know what your code is really doing.

My only advice is learn to use a debugger and use it on your code, you will learn a lot this way. You will see with time that this 'Debug' Knowledge is priceless.

If you don't have a Debugger handy, Try to follow by hand how a,b and c evolve as your program run.

By the way, First thing to do is doing the mathematical analyse, you will see that all solutions follow a given curve, this curve should be the starting point of your programming.

You may not like my answer today, give it a try and you will see if I am wrong.

help with java code for project euler

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