CODEWITHSUNDEEP
javajava-stream
Daniel
Daniel

Reputation: 13

Sum Array if a condition is met

I want to sum (running sum) the values of an int Array and put the result in new array on corresponding position. If sum <0, result should be 0. I'm trying to find a better way to write below code? Maybe with streams java8?

    int[] originalArray = {3,7,-12,1,8,5};
    int[] resultArray= new int[originalArray.length];

    resultArray[0]=(originalArray[0]<0) ? 0:originalArray[0];

    for(int i=1;i<originalArray.length;i++){
        int sum=resultArray[i-1]+originalArray[i];
        resultArray[i]=(sum<0) ? 0 : sum;          
    //    System.out.println(resultArray[i]);        
    }

Upvotes: 0

Views: 346

Answers (1)

Lino
Lino

Reputation: 19926

You don't need streams for this, a simple loop like you've already used is enough:

for (int i = 0, previous = 0; i < originalArray.length; i++) {
    previous = resultArray[i] = Math.max(originalArray[i] + previous, 0);
}

You see that I introduced two things:

  • previous: a helper variable, which tracks the previous result

  • Math.max(): a useful method, it allows us to pick the result if it is positive or else 0 when it is negative (0 is greater than any negative)

    The method looks something like this, which is exactly what you've done already:

    public static int max(int a, int b) {
    return (a >= b) ? a : b;
}

If you don't like the multiple assignment line:

previous = resultArray[i] = Math.max(originalArray[i] + previous, 0);

Then you could also write it like this, if that's more understandable:

previous = Math.max(originalArray[i] + previous, 0);
resultArray[i] = previous;

Upvotes: 3

Related Questions