Multiplying adjacent elements and compare which has a higher value

Question

I am trying to compare which has a greater quotient when multiplying adjacent elements:

public static void main(String args[]) {
    int[] inputArray = {-5, 8, -9, 1, -5, 4};
    int x = 0;
    long maxsofar = 0;
    while (x < inputArray.length - 1) {
        int currentmax = inputArray[x] * inputArray[x + 1];
        maxsofar = (maxsofar > currentmax) ? maxsofar : currentmax;
        }
        x++;
    }
    System.out.println(maxsofar);
}

So far my code works, but when I try to use negative integers on my array, it just outputs 0.

change `long maxsofar = 0` with `long maxofar = Long.MIN_VALUE;` — zlakad, Apr 27 '18 at 14:10
just to short your code instead of if(maxsofar>currentmax)::::::::::::::::::: use if(maxsofar — bit-shashank, Apr 27 '18 at 14:12
Or if he already knows the numbers in advance he can calculate that on a sheet of paper and make it even shorter : maxsofar=0! — Veselin Davidov, Apr 27 '18 at 14:13
OMG i did not see that.. thanks soo much guys.. i didn't realize that i initialized my maxsofar to 0. — George, Apr 27 '18 at 14:17
What, in the context of `Multiplying adjacent elements` is `a greater quotient` / `a higher value`? — greybeard, Apr 28 '18 at 11:54

Veselin Davidov · Accepted Answer · 2018-04-27T14:14:19.547

That's probably because 0 is > than negative numbers. All your adjacent elements when multiplied create negative numbers->

-5*8=-40

8*-9=-72

etc.

So 0 is the maximum one.

You can use Math.abs() for example to use the absolute value. Or you can set maxsofar to the Long.MIN_VALUE to get the largest number even if negative. The way you have done it you get the largest number > 0.

And also this way your program works for exactly that array (having 5 elemtents). A nicer way would be:

for (int i = 0; i < inputArray.length - 2; i++) {
            int currentmax = inputArray[i] * inputArray[i + 1];
            if (maxsofar < currentmax) {                
                maxsofar = currentmax;
            } //No need to handle the case where you say A=A :)
        }

Or even better you can do Math.max(maxsofar,currentmax);

stephan f · Answer 2 · 2018-04-27T15:25:18.793

0

Try using:

long maxsofar = Long.MIN_VALUE;

as initialization. Then the next max is guaranteed to be larger.

edited Apr 27 '18 at 15:25

answered Apr 27 '18 at 14:11

stephan f

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This creates an error cannot find symbol. The constant is Long.MIN_VALUE. – Xypron Apr 27 '18 at 14:23

Multiplying adjacent elements and compare which has a higher value

2 Answers2