Finding max in an array using recursion

Question

Suppose I have the following declarations:

int arr[5] = {1,10,9,28,3};
int low = 0;
int high = 4; 
int largest = findLargest(ar, low, high);

I am suppose to write a "findLargest" function using recursion, and this is what I got

 int findLargest(int arr[], int low, int high)
 {      
    if (low == high)
        return arr[low];
    return max(arr[low], findLargest(arr, low+1, high));
 }

The output was 28, which was expected. However, I don't really understand how does this recursive function "compare" the values. (By that I mean I don't see any operators such as >, <. The only operator that I see is ==). So, how does this recursive function compare the values in the array?

Think about what happens when you call this function with an array that has only one element. Simple, right? Then think about what happens when you call it with an array that has two elements. Then three, then four, etc. — Pete Becker
– Pete Becker, Commented Oct 17, 2016 at 21:11

Matthieu M. · Accepted Answer · 2016-10-18 12:35:59Z

6

The recursion is using the std::max function, which uses operator<. The maximum of the subarray [a;b] is the maximum between a and the maximum of the subarray [a + 1;b] (Which is a if a = b).

edited Oct 18, 2016 at 12:35

Matthieu M.

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answered Oct 17, 2016 at 20:50

Balthazar

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