<p>You are given an integer array <code>nums</code> and an integer <code>k</code>.</p>

<p>In one operation, you can pick two numbers from the array whose sum equals <code>k</code> and remove them from the array.</p>

<p>Return <em>the maximum number of operations you can perform on the array</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> nums = [1,2,3,4], k = 5
<strong>Output:</strong> 2
<strong>Explanation:</strong> Starting with nums = [1,2,3,4]:
- Remove numbers 1 and 4, then nums = [2,3]
- Remove numbers 2 and 3, then nums = []
There are no more pairs that sum up to 5, hence a total of 2 operations.</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> nums = [3,1,3,4,3], k = 6
<strong>Output:</strong> 1
<strong>Explanation:</strong> Starting with nums = [3,1,3,4,3]:
- Remove the first two 3&#39;s, then nums = [1,4,3]
There are no more pairs that sum up to 6, hence a total of 1 operation.</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>1 &lt;= nums[i] &lt;= 10<sup>9</sup></code></li>
	<li><code>1 &lt;= k &lt;= 10<sup>9</sup></code></li>
</ul>

class Solution {
public:
    int maxOperations(vector<int>& nums, int k) {
        int count=0;
        auto radixSort = [](std::vector<int>& arr) {
            int max_num = *std::max_element(arr.begin(), arr.end());
            int exp = 1;
            std::vector<int> output(arr.size());
            
            while (max_num / exp > 0) {
                std::vector<int> count(10, 0);

                for (int i = 0; i < arr.size(); i++) {
                    count[(arr[i] / exp) % 10]++;
                }

                for (int i = 1; i < 10; i++) {
                    count[i] += count[i - 1];
                }

                for (int i = arr.size() - 1; i >= 0; i--) {
                    output[count[(arr[i] / exp) % 10] - 1] = arr[i];
                    count[(arr[i] / exp) % 10]--;
                }

                for (int i = 0; i < arr.size(); i++) {
                    arr[i] = output[i];
                }

                exp *= 10;
            }
        };
        radixSort(nums);
        int left=0;
        int right=nums.size()-1;
        while (left<right)
        {
            if(nums[left]+nums[right]==k)
            {
                count++;
                left++;
                right--;
            }
            else if (nums[left]+nums[right]<k)
            {
                left++;
            }
            else
            {
                right--;
            }
        }
        return count;
}
       
};
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