力扣540.有序数组中的单一元素

• 找到 偶数位做二分

  • 若不等 说明当前mid在单一元素右侧 r = mid
  • 若相等 说明当前mid在单一元素左侧 l = mid + 2

•   class Solution {
    public:
        int singleNonDuplicate(vector<int>& nums) {
            int l = 0,r = nums.size() -1;
            while(l<r)
            {
                int mid = l + r >> 1;
                if(mid % 2 == 1) mid --;
                if(nums[mid] == nums[mid+1]) l = mid+2;
                else r = mid;
            }
            return nums[l];
        }
    };