1679. Max Number of K-Sum Pairs

You are given an integer array nums and an integer k.

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

Return the maximum number of operations you can perform on the array.

 

Example 1:

Input: nums = [1,2,3,4], k = 5
Output: 2
Explanation: 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.

Example 2:

Input: nums = [3,1,3,4,3], k = 6
Output: 1
Explanation: Starting with nums = [3,1,3,4,3]:
- Remove the first two 3's, then nums = [1,4,3]
There are no more pairs that sum up to 6, hence a total of 1 operation.

 

Constraints:

• 1 <= nums.length <= 105
• 1 <= nums[i] <= 109
• 1 <= k <= 109

class Solution {
    public int maxOperations(int[] nums, int k) {
        Arrays.sort(nums);

        int output = 0;
        int left = 0;
        int right = nums.length-1;
        while(left<right){
            if(nums[left]+nums[right]==k){
                output++;
                left++;
                right--;
            }else if(nums[left]+nums[right]<k){
                left++;
            }else{
                right--;
            }
        }
        return output;
    }
}

 

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