3168. Minimum Number of Chairs in a Waiting Room

You are given a string s. Simulate events at each second i:

• If s[i] == 'E', a person enters the waiting room and takes one of the chairs in it.
• If s[i] == 'L', a person leaves the waiting room, freeing up a chair.

Return the minimum number of chairs needed so that a chair is available for every person who enters the waiting room given that it is initially empty.

class Solution {
public:
    int minimumChairs(string s) {
        int res = 0, now = 0;
        for(auto& ch : s) {
            if(ch == 'E') now++;
            else now--;
            res = max(res, now);
        }
        return res;
    }
};