Tuesday, June 8, 2010

Perfect Cubes

For hundreds of years Fermat's Last Theorem, which stated simply that for n > 2 there exist no integers a, b, c > 1 such that an+bn+cn, has remained elusively unproven. (A recent proof is believed to be correct, though it is still undergoing scrutiny.) It is possible, however, to find integers greater than 1 that satisfy the ``perfect cube'' equation a3=b3+c3+d3 (e.g. a quick calculation will show that the equation 123=63+83+103 is indeed true). This problem requires that you write a program to find all sets of numbers {a, b, c, d} which satisfy this equation for a<=200.


Output


The output should be listed as shown below, one perfect cube per line, in non-decreasing order of a (i.e. the lines should be sorted by their a values). The values of b, c, and d should also be listed in non-decreasing order on the line itself. There do exist several values of a which can be produced from multiple distinct sets of b, c, and d triples. In these cases, the triples with the smaller b values should be listed first.


The first part of the output is shown here:


Cube = 6, Triple = (3,4,5)


Cube = 12, Triple = (6,8,10)


Cube = 18, Triple = (2,12,16)


Cube = 18, Triple = (9,12,15)


Cube = 19, Triple = (3,10,18)


Cube = 20, Triple = (7,14,17)


Cube = 24, Triple = (12,16,20)

 


using System;


using System.Collections.Generic;


using System.Linq;


using System.Text;


 


namespace Cubes


{


    class Program


    {


        static void Main(string[] args)


        {


            for (int i = 6; i < 200; i++)


            {


                for (int j = 2; j < 200; j++)


                {


                    for (int k = j + 1; k < 200; k++)


                    {


                        for (int l = k + 1; l < 200; l++)


                        {


                            if ((i*i*i) == (j*j*j) + (k*k*k) + (l*l*l))


                            {


                                Console.WriteLine(i +" "+ j +" "+ k +" "+ l);


                            }


                        }


                    }


                }


            }


        }


    }


}

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