GFG PTOD | 05 Jan 2025 | Count Pairs whose sum is less than target

int countPairs(vector<int> &arr, int target) {
        // Your code here
        sort(arr.begin(), arr.end());
        int count=0, l=0, r=arr.size()-1;
        while(l<r) {
            int sum = arr[l]+arr[r];
            if(sum < target) {
                count += r-l;
                l++;
            } else {
                r--;
            }
        }
        return count;
    }