beats 100% and easy solution in cpp.
IntuitionApproachComplexity
Time complexity:O(n^2)

Space complexity:O(1)
Code
# Intuition
<!-- Describe your first thoughts on how to solve this problem. -->

# Approach
<!-- Describe your approach to solving the problem. -->

# Complexity
- Time complexity:O(n^2)
<!-- Add your time complexity here, e.g. $$O(n)$$ -->

- Space complexity:O(1)
<!-- Add your space complexity here, e.g. $$O(n)$$ -->

# Code
```cpp []
class Solution {
public:
    int countPairs(vector<int>& nums, int target) {
        int res=0;
        for(int j=0;j<nums.size();j++)
        {
            for(int k=j+1;k<nums.size();k++)
            {
                if(nums[j]+nums[k]<target)
                {
                    res++;
                }
            }
        }
        return res;
    }
};
```
['Array', 'Two Pointers', 'C++']