1450. Number of Students Doing Homework at a Given Time

Given two integer arrays startTime and endTime and given an integer queryTime.

The ith student started doing their homework at the time startTime[i] and finished it at time endTime[i].

Return the number of students doing their homework at time queryTime. More formally, return the number of students where queryTime lays in the interval [startTime[i], endTime[i]] inclusive.

Example 1:

Input: startTime = [1,2,3], endTime = [3,2,7], queryTime = 4
Output: 1
Explanation: We have 3 students where:
The first student started doing homework at time 1 and finished at time 3 and wasn't doing anything at time 4.
The second student started doing homework at time 2 and finished at time 2 and also wasn't doing anything at time 4.
The third student started doing homework at time 3 and finished at time 7 and was the only student doing homework at time 4.

Example 2:

Input: startTime = [4], endTime = [4], queryTime = 4
Output: 1
Explanation: The only student was doing their homework at the queryTime.

Example 3:

Input: startTime = [4], endTime = [4], queryTime = 5
Output: 0

Example 4:

Input: startTime = [1,1,1,1], endTime = [1,3,2,4], queryTime = 7
Output: 0

Example 5:

Input: startTime = [9,8,7,6,5,4,3,2,1], endTime = [10,10,10,10,10,10,10,10,10], queryTime = 5
Output: 5

Constraints:

• startTime.length == endTime.length
• 1 <= startTime.length <= 100
• 1 <= startTime[i] <= endTime[i] <= 1000
• 1 <= queryTime <= 1000

class Solution {
    public int busyStudent(int[] startTime, int[] endTime, int queryTime) {
        Map<Integer, Integer> map = new HashMap();
        int le = startTime.length;
        int res = 0;
        for(int i = 0; i < le; i++){
            if(startTime[i] <= queryTime) map.put(i, startTime[i]);
        }
        List<Integer> list = new ArrayList(map.keySet());
        for(int i = 0; i < list.size(); i++){
            if(endTime[(int)list.get(i)] >= queryTime) res++;
        }
        return res;
    }
}

要求：startTime必须小于等于queryTime，endTime必须大于等于queryTime即可