1450. Number of Students Doing Homework at a Given Time

Description

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.

 

Constraints:

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

Solutions

Solution 1

Python Code
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class Solution:
    def busyStudent(
        self, startTime: List[int], endTime: List[int], queryTime: int
    ) -> int:
        return sum(a <= queryTime <= b for a, b in zip(startTime, endTime))

Java Code
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class Solution {
    public int busyStudent(int[] startTime, int[] endTime, int queryTime) {
        int ans = 0;
        for (int i = 0; i < startTime.length; ++i) {
            if (startTime[i] <= queryTime && queryTime <= endTime[i]) {
                ++ans;
            }
        }
        return ans;
    }
}

C++ Code
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class Solution {
public:
    int busyStudent(vector<int>& startTime, vector<int>& endTime, int queryTime) {
        int ans = 0;
        for (int i = 0; i < startTime.size(); ++i) {
            ans += startTime[i] <= queryTime && queryTime <= endTime[i];
        }
        return ans;
    }
};

Go Code
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func busyStudent(startTime []int, endTime []int, queryTime int) int {
	ans := 0
	for i, a := range startTime {
		b := endTime[i]
		if a <= queryTime && queryTime <= b {
			ans++
		}
	}
	return ans
}

TypeScript Code
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function busyStudent(startTime: number[], endTime: number[], queryTime: number): number {
    const n = startTime.length;
    let res = 0;
    for (let i = 0; i < n; i++) {
        if (startTime[i] <= queryTime && endTime[i] >= queryTime) {
            res++;
        }
    }
    return res;
}

Rust Code
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impl Solution {
    pub fn busy_student(start_time: Vec<i32>, end_time: Vec<i32>, query_time: i32) -> i32 {
        let mut res = 0;
        for i in 0..start_time.len() {
            if start_time[i] <= query_time && end_time[i] >= query_time {
                res += 1;
            }
        }
        res
    }
}

C Code
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int busyStudent(int* startTime, int startTimeSize, int* endTime, int endTimeSize, int queryTime) {
    int res = 0;
    for (int i = 0; i < startTimeSize; i++) {
        if (startTime[i] <= queryTime && endTime[i] >= queryTime) {
            res++;
        }
    }
    return res;
}

Solution 2

Python Code
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class Solution:
    def busyStudent(
        self, startTime: List[int], endTime: List[int], queryTime: int
    ) -> int:
        c = [0] * 1010
        for a, b in zip(startTime, endTime):
            c[a] += 1
            c[b + 1] -= 1
        return sum(c[: queryTime + 1])

Java Code
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class Solution {
    public int busyStudent(int[] startTime, int[] endTime, int queryTime) {
        int[] c = new int[1010];
        for (int i = 0; i < startTime.length; ++i) {
            c[startTime[i]]++;
            c[endTime[i] + 1]--;
        }
        int ans = 0;
        for (int i = 0; i <= queryTime; ++i) {
            ans += c[i];
        }
        return ans;
    }
}

C++ Code
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class Solution {
public:
    int busyStudent(vector<int>& startTime, vector<int>& endTime, int queryTime) {
        vector<int> c(1010);
        for (int i = 0; i < startTime.size(); ++i) {
            c[startTime[i]]++;
            c[endTime[i] + 1]--;
        }
        int ans = 0;
        for (int i = 0; i <= queryTime; ++i) {
            ans += c[i];
        }
        return ans;
    }
};

Go Code
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func busyStudent(startTime []int, endTime []int, queryTime int) int {
	c := make([]int, 1010)
	for i, a := range startTime {
		b := endTime[i]
		c[a]++
		c[b+1]--
	}
	ans := 0
	for i := 0; i <= queryTime; i++ {
		ans += c[i]
	}
	return ans
}