leetcode

0 class Solution {

1 static long long countLess(const vector<int> &nums, int target) {

2 long long res = 0;

3

4 for (int i = 0, j = size(nums) - 1; i < j; i++) {

5 while (i < j && nums[i] + nums[j] > target)

6 j--;

7 res += j - i;

8 }

9

10 return res;

11 }

12

13 public:

14 long long countFairPairs(vector<int> &nums, int lower, int upper) const {

15 sort(begin(nums), end(nums));

16 return countLess(nums, upper) - countLess(nums, lower - 1);

17 }

18 };