// This class shows an example of how to use binary search
import java.util.Arrays;

public class BinarySearch {
    public static void main(String[] args) {
        int[] arr = {-4, 2, 7, 10, 15, 20, 22, 25, 30, 36, 42, 50, 56, 68, 85, 92, 103};
        System.out.println("Our binary search: " + binarySearch(arr, 42));
        System.out.println("Java's binary search: " + Arrays.binarySearch(arr, 42));
    }

    // pre: The array is sorted
    // post: Returns the index of the first occurence of val in arr, -1 if not found
    public static int binarySearch(int[] arr, int val) {
        int low = 0;
        int high = arr.length - 1;

        // Keep going while the high and low pointers haven't moved past each other
        while(high >= low) {
            int middle = (low + high) / 2;
            if (arr[middle] == val) {
                return middle; // we found it!
            } else if (arr[middle] < val) {
                low = middle + 1;
            } else { // arr[middle] > val
                high = middle - 1;
            }
        }
        return -1; // not found
    }
}