offer2-70

给定一个只包含整数的有序数组 nums ，每个元素都会出现两次，唯有一个数只会出现一次，请找出这个唯一的数字。

你设计的解决方案必须满足 O(log n) 时间复杂度和 O(1) 空间复杂度。

示例 1:

输入: nums = [1,1,2,3,3,4,4,8,8]
输出: 2

示例 2:

输入: nums =  [3,3,7,7,10,11,11]
输出: 10

提示:

• 1 <= nums.length <= 105
• 0 <= nums[i] <= 105

//leetcode submit region begin(Prohibit modification and deletion)
class Solution {

    public int singleNonDuplicate(int[] nums) {
        int start = 0;
        int end = nums.length - 1;

        while (start <= end) {
            if (start == end) {
                return nums[start];
            }

            int mid = start + (end - start) / 2;
            if (nums[mid - 1] == nums[mid]) {
                if ((mid + 1) % 2 == 0) {
                    start = mid + 1;
                } else {
                    end = mid;
                }
            } else if (nums[mid + 1] == nums[mid]) {
                if ((mid + 2) % 2 == 0) {
                    start = mid + 2;
                } else {
                    end = mid - 1;
                }
            } else {
                return nums[mid];
            }
        }

        return -1;
    }
}
//leetcode submit region end(Prohibit modification and deletion)