lintcode585- Maximum Number in Mountain Sequence- medium

public class Solution {
    /*
     * @param nums: a mountain sequence which increase firstly and then decrease
     * @return: then mountain top
     */
    public int mountainSequence(int[] nums) {

        // 要怎么处理输入？？？
        if (nums == null || nums.length == 0){
            throw new IllegalArgumentException();
        }

        int start = 0;
        int end = nums.length - 1;

        while (start + 1 < end){
            int mid = start + (end - start) / 2;
            // 应该不用判断mid < nums.length - 1把，天然的。
            // 等于情况似乎无法处理，输入应该这种描述不会给吧
            if (nums[mid + 1] - nums[mid] > 0){
                start = mid;
            } else {
                end = mid;
            }
        }

        if (nums[start] > nums[end]){
            return nums[start];
        }

        return nums[end];

    }
}