Why does it keep returning false?

Question

I tried my best to return int number as a perfect cube without declaring it. I don't know what I'm doing wrong. The assignment: TODO: Return true if number is a perfect cube, false otherwise. You can assume the value of number is between 1 and 1000000

Note: a perfect cube is a number whose cube root is an integer

   static boolean Q1(int number) {
    int a = number/9;


    if(number==(a*a*a))
    {
        return true;

    } else {
        return false;
    }
    // TODO: Return true if number is a perfect cube, false otherwise. You can assume the value
    //       of number is between 1 and 1000000
    //
    // Note: a perfect cube is a number whose cube root is an integer




}






ERROR:

-- Q1 --
Incorrect on input: 8
Expected output : true
Your output     : false

`int s = number/3;` is doing integer division e.g. `1/2 == 0` try `double s = number/3.0` — Scary Wombat, Feb 27 '17 at 02:52
The assigned so called duplicate question has nothing to do with my question. — Nar, Feb 27 '17 at 03:03
Your formula is wrong. Dividing a number by 9 doesn't produce a cube root, except for 27. — shmosel, Feb 27 '17 at 03:12
@ScaryWombat You can only say integer division is wrong in the context of the problem and solution. If we were trying to find a number evenly divisible by 3, integer division could make perfect sense. Since OP's solution has little to do with the problem, it's hard to pass judgement on a detail of it. — shmosel, Feb 27 '17 at 03:19
Why would the cuberoot be `number / 9` ? There are only three integers for which this is true. — Dawood ibn Kareem, Feb 27 '17 at 03:52

score 0 · Answer 1 · answered Feb 27 '17 at 03:32

int s = number/3;
int a = s/3;

So a is now number/9

if( number==(a*a*a))

And here you check whether number is equal to (number*number*number)/729. How is that supposed to mean anything?

You really need to figure out your algorithm before you start to code a single line.

Why does it keep returning false?

1 Answers1