Finding the minimum of an array using recursion?

java recursion minimum
Vance picture Vance · Apr 9, 2011 · Viewed 33.6k times · Source

Ok, so I've been trying to wrap my head around recursion in Java and I can accomplish easy tasks such as sum, reversing etc. but I have been struggling to do this exercise:

I'm trying to find the minimum number in an array using recursion but keep getting an answer of 0.0.

My understanding for recursion is that there I need to increment one element and then provide a base case that will end the recursion. I think I'm messing up when I have to return a value and when is best to call the recursion method.

This is what I have so far:

public static double findMin(double[] numbers, int startIndex, int endIndex) {

double min;
int currentIndex = startIndex++;

if (startIndex == endIndex)
    return numbers[startIndex];

else {
    min = numbers[startIndex];
    if (min > numbers[currentIndex]) {
        min = numbers[currentIndex];
        findMin(numbers, currentIndex, endIndex);
    }
            return min;
}       
} //findMin

Answer

Gareth McCaughan picture Gareth McCaughan · Apr 9, 2011

Hint: You're calling findMin recursively, but then not using its return value.

What's the relationship between (1) the min of the whole array, (2) the first element, and (3) the min of everything apart from the first element?

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