Java - Find largest number in array using recursion

Question

I'm trying to use recursion to find the largest number in the array, but am not getting the results i hoped. Any help would be very appreciated.

public class ArrayMax {
    public static int largestInteger(int[] array) {

        return FindlargestInteger(array, 0, -99999999);

    }   

    public static int FindlargestInteger(int[] array, int index, int max) { 

        if (index == array.length)
            return max;

        if (array[index] > max) {
            max = array[index];
        }

        FindlargestInteger(array, index + 1, max);

        return max;     
    }
}

Sidebar comment: use Integer.MIN_VALUE instead of -99999999 — Ceelos
– Ceelos, Commented Mar 21, 2016 at 22:04

Yassin Hajaj · Accepted Answer · 2016-03-21 22:03:41Z

5

You need to return a call to the function for your function to be recursive.

return FindlargestInteger(array, index + 1,max);

Code

public static int FindlargestInteger(int[] array, int index,int max){   
    if(index == array.length)
        return max;

    if (array[index] > max){
        max = array[index];
    }
    return FindlargestInteger(array, index + 1,max);
}

answered Mar 21, 2016 at 22:03

Yassin Hajaj

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Comments

Elliott Frisch · Accepted Answer · 2016-03-21 22:08:10Z

Your FindlargestInteger method doesn't currently recurse. You need to first start with a base case; if you're at the end of the array return the last element; otherwise return the largest of the element at the current index or the result of recursing. And, you don't need to pass max into the function. You can do it with something like¹,

public static int FindlargestInteger(int[] array, int index) {
    if (index < array.length - 1) {
        return Math.max(array[index], FindlargestInteger(array, index + 1));
    }
    return array[array.length - 1];
}

If the goal wasn't recursion, and you're using Java 8+, you might also implement it with a one line method using an IntStream like

return IntStream.of(array).max();

^{1_{Please follow Java method naming conventions, method names should start with a lower case letter. As is, your method looks like a constructor.}}

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