Write a JAVA program to check if the given number is a Hardy Ramanujan Number. basic way :)
Answers
Compilation: javac Ramanujan.java
* Execution: java Ramanujan n
*
* Prints out any number between 1 and n that can be expressed as the
* sum of two cubes in two (or more) different ways.
*
* % java Ramanujan 1728
*
* % java Ramanujan 1729
* 1729 = 1^3 + 12^3 = 9^3 + 10^3
*
* % java Ramanujan 10000
* 1729 = 1^3 + 12^3 = 9^3 + 10^3
* 4104 = 2^3 + 16^3 = 9^3 + 15^3
*
* % java Ramanujan 100000
* 1729 = 1^3 + 12^3 = 9^3 + 10^3
* 4104 = 2^3 + 16^3 = 9^3 + 15^3
* 13832 = 2^3 + 24^3 = 18^3 + 20^3
* 39312 = 2^3 + 34^3 = 15^3 + 33^3
* 46683 = 3^3 + 36^3 = 27^3 + 30^3
* 32832 = 4^3 + 32^3 = 18^3 + 30^3
* 40033 = 9^3 + 34^3 = 16^3 + 33^3
* 20683 = 10^3 + 27^3 = 19^3 + 24^3
* 65728 = 12^3 + 40^3 = 31^3 + 33^3
* 64232 = 17^3 + 39^3 = 26^3 + 36^3
*
* % java Ramanujan 100000000 | sort -n // sort results numerically in Unix
* 1729 = 1^3 + 12^3 = 9^3 + 10^3
* ...
* 87539319 = 167^3 + 436^3 = 228^3 + 423^3
* 87539319 = 167^3 + 436^3 = 255^3 + 414^3
* 87539319 = 228^3 + 423^3 = 255^3 + 414^3
* ...
*
* Bugs
* ----
* If a number can be expressed as a sum of cubes in more than two
* different ways, the program prints some duplicates.
*
******************************************************************************/
public class Ramanujan {
public static void main(String[] args) {
// read in one command-line argument
int n = Integer.parseInt(args[0]);
// for each a, b, c, d, check whether a^3 + b^3 = c^3 + d^3
for (int a = 1; a <= n; a++) {
int a3 = a*a*a;
if (a3 > n) break;
// start at a to avoid print out duplicate
for (int b = a; b <= n; b++) {
int b3 = b*b*b;
if (a3 + b3 > n) break;
// start at a + 1 to avoid printing out duplicates
for (int c = a + 1; c <= n; c++) {
int c3 = c*c*c;
if (c3 > a3 + b3) break;
// start at c to avoid printing out duplicates
for (int d = c; d <= n; d++) {
int d3 = d*d*d;
if (c3 + d3 > a3 + b3) break;
if (c3 + d3 == a3 + b3) {
System.out.print((a3+b3) + " = ");
System.out.print(a + "^3 + " + b + "^3 = ");
System.out.print(c + "^3 + " + d + "^3");
System.out.println();
}
}
}
}
}
}
}
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Last updated: Fri Oct 20 14:12:12 EDT 2017.