1
vector<vector<int>> intervalIntersection(vector<vector<int>>& A, vector<vector<int>>& B) {
2
    vector<vector<int>> res;
3
    int i = 0, j = 0;
4
    while(i < A.size() && j < B.size()) {
5
        // check A[i] and B[j]
6
        int left = max(A[i][0], B[j][0]), right = min(A[i][1], B[j][1]);
7
        if (left <= right) res.push_back({left, right});
8
        // update i and j
9
        if (A[i][1] > B[j][1]) j++;
10
        else if (A[i][1] < B[j][1]) i++;
11
        else {
12
            i++; j++;
13
        }
14
    }
15

2 collapsed lines
16
    return res;
17
}