<p>You are given a sorted array consisting of only integers where every element appears exactly twice, except for one element which appears exactly once.</p>

<p>Return <em>the single element that appears only once</em>.</p>

<p>Your solution must run in <code>O(log n)</code> time and <code>O(1)</code> space.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<pre><strong>Input:</strong> nums = [1,1,2,3,3,4,4,8,8]
<strong>Output:</strong> 2
</pre><p><strong class="example">Example 2:</strong></p>
<pre><strong>Input:</strong> nums = [3,3,7,7,10,11,11]
<strong>Output:</strong> 10
</pre>
<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= nums.length &lt;= 10<sup>5</sup></code></li>
	<li><code>0 &lt;= nums[i] &lt;= 10<sup>5</sup></code></li>
</ul>

class Solution {
public:
    int singleNonDuplicate(vector<int>& nums) {
        int n=nums.size();
        int l=0,r=n-1;
        while(l<r)
        {
            int mid=(l+r)/2;
            if(nums[mid]==nums[mid-1])
            {
                int ctl=mid-l+1;
                int ctr=r-mid;
                if(ctl%2!=0)
                {
                   r=mid;
                }
                else{
                    l=mid+1;
                }
            }
            else if(nums[mid]==nums[mid+1])
            {
                int ctl=mid-l;
                int ctr=r-mid+1;
                if(ctl%2!=0)
                {
                   r=mid-1;
                }
                else{
                    l=mid;
                }
            }
            else
            {
                return nums[mid];
            }
        }
        return nums[l];
    }
};
25000