题目

地址

https://leetcode.com/problems/minimum-number-of-chairs-in-a-waiting-room/description/

内容

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.

Example 1:

Input: s = “EEEEEEE”
Output: 7
Explanation:
After each second, a person enters the waiting room and no person leaves it. Therefore, a minimum of 7 chairs is needed.

Example 2:

Input: s = “ELELEEL”
Output: 2
Explanation:
Let’s consider that there are 2 chairs in the waiting room. The table below shows the state of the waiting room at each second.

Second	Event	People in the Waiting Room	Available Chairs
0	Enter	1	1
1	Leave	0	2
2	Enter	1	1
3	Leave	0	2
4	Enter	1	1
5	Enter	2	0
6	Leave	1	1

Example 3:

Input: s = “ELEELEELLL”
Output: 3
Explanation:
Let’s consider that there are 3 chairs in the waiting room. The table below shows the state of the waiting room at each second.

Second	Event	People in the Waiting Room	Available Chairs
0	Enter	1	2
1	Leave	0	3
2	Enter	1	2
3	Enter	2	1
4	Leave	1	2
5	Enter	2	1
6	Enter	3	0
7	Leave	2	1
8	Leave	1	2
9	Leave	0	3

Constraints:

• 1 <= s.length <= 50
• s consists only of the letters ‘E’ and ‘L’.
• s represents a valid sequence of entries and exits.

解题

这题就是模拟一个队列，E代表如队列，L代表出队列。然后按照字符串中的EL的信息，计算出这个队列最长时是多长。
我们不用使用队列或者栈这样的数据结构，直接使用计数器来做就行了。

#include <string>
#include <stack>
using namespace std;

class Solution {
public:
    int minimumChairs(string s) {
        int maxChairs = 0;
        stack<int> chairs;
        for (char c : s) {
            if (c == 'L') {
                chairs.pop();
            } else {
                chairs.push(1);
                maxChairs = max(maxChairs, (int)chairs.size());
            }
        }
        return maxChairs;
    }
};

代码地址

https://github.com/f304646673/leetcode/tree/main/3168-Minimum-Number-of-Chairs-in-a-Waiting-Room/cplusplus