题解 | #农场牛类别匹配#

import java.util.*;


public class Solution {
    public  int countMatchingPairs (int[] breeds, int target_sum) {
        int len = breeds.length;
        int left = 0, right = breeds.length - 1, count = 0;//定义双指针
        Arrays.sort(breeds);
        while (left < right) {
            if (breeds[left] + breeds[right] < target_sum) {
                left++;
            } else if (breeds[left] + breeds[right] > target_sum) {
                right--;
            } else {
                count++;
                left++;
                right--;//因为要分组，所以不用重复，直接左加右减
            }
        }
        return count;
    }
}