每次弃一半，所以是lg(n)

class Solution {
    public int search(int[] nums, int target) {
        if (nums == null || nums.length == 0) return -1;

        int low = 0, high = nums.length - 1;

        while (low <= high){
            int mid = low + (high - low) / 2;

            if (nums[mid] == target) return mid;

            if (nums[low] <= nums[mid]){
                if (target >= nums[low] && target < nums[mid]){
                    high = mid - 1;
                }
                else{
                    low = mid + 1;
                }
            }
            else{
                if (target > nums[mid] && target <= nums[high]){
                    low = mid + 1;
                }
                else{
                    high = mid - 1;
                }
            }
        }

        return -1;
    }
}