Count Integers in Intervals LeetCode solution in C++

1
class CountIntervals {
2
  set<pair<int, int>> st;
3
  int cnt;
4

5
 public:
6
  CountIntervals() {
7
    cnt = 0;
8
  }
9

10
  void add(int left, int right) {
11
    auto it = st.upper_bound({left, INT_MIN});
12

13
    if (it != st.begin() && (--it)->second < left) {
14
      ++it;
15
    }
16

17
    while (it != st.end() && it->first <= right) {
18
      left = min(left, it->first);
19
      right = max(right, it->second);
20

21
      cnt -= (it->second - it->first + 1);
22
      it = st.erase(it);
23
    }
24

25
    st.insert({left, right});
26
    cnt += (right - left + 1);
27
  }
28

29
  int count() {
30
    return cnt;
31
  }
32
};