1450. Number of Students Doing Homework at a Given Time

#### QUESTION:

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 = , endTime = , queryTime = 4
Output: 1
Explanation: The only student was doing their homework at the queryTime.
``````

Example 3:

``````Input: startTime = , endTime = , 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
``````

#### EXPLANATION:

1. 定义一个数组，用来表示时间点上有多少同学在学习
2. 遍历数组，如果start和end相等的话，只需要将time[start]++就可以
3. 如果不相等的话，则需要将time[start]->times[end]都进行++，来表示有同学在学习
4. 直接获取到time[queryTime]进行返回

#### SOLUTION:

``````class Solution {
public int busyStudent(int[] startTime, int[] endTime, int queryTime) {
int[] times = new int;
for(int i = 0;i<startTime.length;i++){
int start = startTime[i];
int end = endTime[i];
if(start==end) times[start]++;
else {
for (int j = start;j<=end;j++) times[j]++;
}
}
return times[queryTime];
}
}
``````
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