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Thread: computational number theory

  1. #1
    Junior Member
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    Default computational number theory

    Collapse | Copy Code

    public class CubeSum implements Comparable<CubeSum> {
    private final int sum;
    private final int sum2;
    private final int i;
    private final int j;
    private final int a;
    private final int b;

    public CubeSum(int i, int j,int a, int b) {
    this.sum = i*i*i + j*j*j;
    this.i = i;
    this.j = j;
    this.a = a;
    this.b = b;
    this.sum2 = a * a * a + b * b * b;

    public CubeSum(int w

    public int compareTo(CubeSum that) {
    if (this.sum < that.sum) return -1;
    if (this.sum < that.sum) return +1;
    return 0;

    public String toString() {
    return sum + " = " + i + "^3" + " + " + j + "^3";

    public static void main(String[] args) {

    int N = Integer.parseInt(args[0]);

    // initialize priority queue
    MinPQ<CubeSum> pq = new MinPQ<CubeSum>();
    pq.insert(new CubeSum(0,1);

    for (int i = 0,j = 1; i & j <= N; i+=2,j+=2) {
    pq.insert(new CubeSum(i, i,j,j,));
    if(i>0 && j>1)
    pq.insert(new CubeSum(0,i,0,j);
    for(int i =0;i<N;i++)
    for(int j=i+1;j<N;j++)
    if(pq.sum[i] == pq.sum2[j])
    System.out.println("the sum is" + sum[i] + "and the value of i is" + pq.i + " and j is" + pq.j + "and a is" + pq.a + "and b is " + pq.b

    // find smallest sum, print it out, and update
    while (!pq.isEmpty()) {
    CubeSum s = pq.delMin();



    am now confused on how to use this program to find all distinct integers a, b, c, and d between 0 and 10^6 such that a3 + b3 = c3 + d3, e.g., 1729 = 9^3 + 10^3 = 1^3 + 12^3.
    this is the code i have devised which i think will work,but everytime i run it,i get an error message when i try to iterate through PQ to determine if sum = sum

  2. #2
    Super Moderator Norm's Avatar
    Join Date
    May 2010
    Eastern Florida
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    Default Re: computational number theory

    Please Edit your post and wrap your code with
    to get highlighting and preserve formatting.

    i get an error message
    Please copy the full text of the console with the error message and paste it here.
    If you don't understand my answer, don't ignore it, ask a question.

  3. #3
    Join Date
    Jun 2012
    Left Coast, USA
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    Default Re: computational number theory

    Quote Originally Posted by bojukwu View Post
    ...how to use this program...
    Step 1a: Make changes so that it will compile.

    Step 1b: Include everything in your post that will enable us to compile and execute a program based on this class.

    Unless and until you do that, there is no Step 2. (But if you complete both parts of Step 1, Steps 2 and 3 will be: Follow Norm's suggestions..)


    Last edited by Zaphod_b; July 30th, 2012 at 02:00 PM.

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