Finding the maximum element in a unimodal array (elements increases to a maximum and decreases there after). Efficient algorithm which runs in O(log n) time.

MaxUnimodalArray.java

public class Main {
    public static void main(String[] args) {
        System.out.println(maxElementInUnimodalArray(new int[]{1, 2, 5, 4, 3})); //Expected 5
        System.out.println(maxElementInUnimodalArray(new int[]{1, 2, 3, 4, 5})); //Expected 5
        System.out.println(maxElementInUnimodalArray(new int[]{5, 4, 3, 2, 1})); //Expected 5
        System.out.println(maxElementInUnimodalArray(new int[]{6})); //Expected 6
    }

    private static int maxElementInUnimodalArray(int[] arr) {
        if (arr == null || arr.length == 0) {
            return -1;
        }
        int low = 0, high = arr.length - 1;
        int mid = 0;
        while (low <= high) {
            mid = (low + high) / 2;
            if ((mid == 0 || arr[mid] > arr[mid - 1]) &&
                    (mid == arr.length - 1 || arr[mid] > arr[mid + 1])) {
                break;
            }
            if (mid > 0 && arr[mid] < arr[mid - 1]) {
                high = mid - 1;
            } else {
                low = mid + 1;
            }
        }
        return arr[mid];
    }
}