585. maximum number in mountain sequence

public class  {
    
     * @param nums: a mountain sequence which increase firstly and then decrease
     * @return: then mountain top
     */
    public int mountainSequence(int[] nums) {
        // write your code here
        if (nums == null || nums.length == 0) {
            return 0;
        }

        int start = 0, end = nums.length - 1;
        while (start + 1 < end) {
            int mid = start + (end - start) / 2;
            if (nums[mid] > nums[mid - 1]) { // target on the right(include mid)
                start = mid;
            } else if (nums[mid] < nums[mid - 1]) { // target on the left(exclude mid)
                end = mid - 1;
            } else {
                 end = mid;//start = mid; 不会出现这种情况，in this case, can't do binary search
            }
        }
        if (nums[start] > nums[end]) {
            return nums[start];
        } else {
            return nums[end];
        }

    }
}