Define a positive number to be isolated if none of the digits in its square are in its cube. For example 69 is n isolated number because 163*163 = 26569 and 163*163*163 = 4330747 and the square does not contain any of the digits 0, 3, 4 and 7 which are the digits used in the cube. On the other hand 162 is not an isolated number because 162*162=26244 and 162*162*162 = 4251528 and the digits 2 and 4 which appear in the square are also in the cube.

Write a function named isIsolated that returns 1 if its argument is an isolated number, it returns 0 if its not an isolated number and it returns -1 if it cannot determine whether it is isolated or not.

I have tried this:

public static int isIsolated (int n) { int square = n*n; int cube = n*n*n; int[] a = new int[7]; int[] b = new int[7]; if(n < 2097151 || n>1){ for(int i=6;i>=0;i--){ int k = square % 10; int l = cube % 10; a[i]= k; b[j]=l; square = square/10; cube = cube/10; } for(int j=a.length-1;j>=0;j++) { for(int m=0;m<j;m++) { if(a[j] == b[m]) return 0; else return 1; } } } return -1; }

but its not working as expected.

I am a beginner pls help me.

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## Answer

There were a number of issues with your code.

You were putting `0`

in the array once the number was exhausted so any number with less than 7 digits would end up with at least one `0`

in teh array and fail your test.

You were leaving the default `0`

in the array so any number with a `0`

in either it’s square or it’s cube would have gone wrong. This code suggests the highest isolated number whose cube will fit into a `long`

is:

31563 is isolated – ^2 = 996222969 ^3 = 31443785570547

// Max digits. private static final int DIGITS = 20; // Indicates an empty digit. private static final int EMPTY = -1; // Max value I can handle. private static final long MAX = (long) Math.cbrt(Long.MAX_VALUE); public static int isIsolated(long n) { if (n > 1 && n < MAX) { long square = n * n; long cube = n * n * n; long[] a = new long[DIGITS]; Arrays.fill(a, EMPTY); long[] b = new long[DIGITS]; Arrays.fill(b, EMPTY); for (int i = 0; i < DIGITS; i++) { if (square > 0) { a[i] = square % 10; square = square / 10; } if (cube > 0) { b[i] = cube % 10; cube = cube / 10; } } for (int i = 0; i < DIGITS; i++) { if (a[i] != EMPTY) { for (int j = 0; j < DIGITS; j++) { if (a[i] == b[j]) { return 0; } } } } return 1; } return -1; } public void test(int n) { System.out.println(n + " is " + (isIsolated(n) == 1 ? "" : "not ") + "isolated"); } public void test() { System.out.println("Hello"); test(1234); test(69); test(162); for (long i = 0; i < MAX; i++) { if (isIsolated(i) == 1) { System.out.println(i + " is isolated - ^2 = " + (i * i) + " ^3 = " + (i * i * i)); } } }