Description#
You are given two string arrays positive_feedback and negative_feedback, containing the words denoting positive and negative feedback, respectively. Note that no word is both positive and negative.
Initially every student has 0 points. Each positive word in a feedback report increases the points of a student by 3, whereas each negative word decreases the points by 1.
You are given n feedback reports, represented by a 0-indexed string array report and a 0-indexed integer array student_id, where student_id[i] represents the ID of the student who has received the feedback report report[i]. The ID of each student is unique.
Given an integer k, return the top k students after ranking them in non-increasing order by their points. In case more than one student has the same points, the one with the lower ID ranks higher.
Example 1:
Input: positive_feedback = ["smart","brilliant","studious"], negative_feedback = ["not"], report = ["this student is studious","the student is smart"], student_id = [1,2], k = 2
Output: [1,2]
Explanation:
Both the students have 1 positive feedback and 3 points but since student 1 has a lower ID he ranks higher.
Example 2:
Input: positive_feedback = ["smart","brilliant","studious"], negative_feedback = ["not"], report = ["this student is not studious","the student is smart"], student_id = [1,2], k = 2
Output: [2,1]
Explanation:
- The student with ID 1 has 1 positive feedback and 1 negative feedback, so he has 3-1=2 points.
- The student with ID 2 has 1 positive feedback, so he has 3 points.
Since student 2 has more points, [2,1] is returned.
Constraints:
1 <= positive_feedback.length, negative_feedback.length <= 1041 <= positive_feedback[i].length, negative_feedback[j].length <= 100- Both
positive_feedback[i] and negative_feedback[j] consists of lowercase English letters. - No word is present in both
positive_feedback and negative_feedback. n == report.length == student_id.length1 <= n <= 104report[i] consists of lowercase English letters and spaces ' '.- There is a single space between consecutive words of
report[i]. 1 <= report[i].length <= 1001 <= student_id[i] <= 109- All the values of
student_id[i] are unique. 1 <= k <= n
Solutions#
Solution 1: Hash Table + Sorting#
We can store the positive words in a hash table $ps$ and the negative words in a hash table $ns$.
Then, we traverse the $report$ and for each student, we store their score in an array $arr$, where each element is a tuple $(t, sid)$, where $t$ represents the student’s score and $sid$ represents the student’s ID.
Finally, we sort the array $arr$ in descending order by score, and if the scores are the same, we sort by ID in ascending order. Then, we take the IDs of the top $k$ students.
The time complexity is $O(n \times \log n + (|ps| + |ns| + n) \times |s|)$, and the space complexity is $O((|ps|+|ns|) \times |s| + n)$. Here, $n$ is the number of students, $|ps|$ and $|ns|$ are the number of positive and negative words, respectively, and $|s|$ is the average length of a word.
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| class Solution:
def topStudents(
self,
positive_feedback: List[str],
negative_feedback: List[str],
report: List[str],
student_id: List[int],
k: int,
) -> List[int]:
ps = set(positive_feedback)
ns = set(negative_feedback)
arr = []
for sid, r in zip(student_id, report):
t = 0
for w in r.split():
if w in ps:
t += 3
elif w in ns:
t -= 1
arr.append((t, sid))
arr.sort(key=lambda x: (-x[0], x[1]))
return [v[1] for v in arr[:k]]
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| class Solution {
public List<Integer> topStudents(String[] positive_feedback, String[] negative_feedback,
String[] report, int[] student_id, int k) {
Set<String> ps = new HashSet<>();
Set<String> ns = new HashSet<>();
for (var s : positive_feedback) {
ps.add(s);
}
for (var s : negative_feedback) {
ns.add(s);
}
int n = report.length;
int[][] arr = new int[n][0];
for (int i = 0; i < n; ++i) {
int sid = student_id[i];
int t = 0;
for (var s : report[i].split(" ")) {
if (ps.contains(s)) {
t += 3;
} else if (ns.contains(s)) {
t -= 1;
}
}
arr[i] = new int[] {t, sid};
}
Arrays.sort(arr, (a, b) -> a[0] == b[0] ? a[1] - b[1] : b[0] - a[0]);
List<Integer> ans = new ArrayList<>();
for (int i = 0; i < k; ++i) {
ans.add(arr[i][1]);
}
return ans;
}
}
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| class Solution {
public:
vector<int> topStudents(vector<string>& positive_feedback, vector<string>& negative_feedback, vector<string>& report, vector<int>& student_id, int k) {
unordered_set<string> ps(positive_feedback.begin(), positive_feedback.end());
unordered_set<string> ns(negative_feedback.begin(), negative_feedback.end());
vector<pair<int, int>> arr;
int n = report.size();
for (int i = 0; i < n; ++i) {
int sid = student_id[i];
vector<string> ws = split(report[i], ' ');
int t = 0;
for (auto& w : ws) {
if (ps.count(w)) {
t += 3;
} else if (ns.count(w)) {
t -= 1;
}
}
arr.push_back({-t, sid});
}
sort(arr.begin(), arr.end());
vector<int> ans;
for (int i = 0; i < k; ++i) {
ans.emplace_back(arr[i].second);
}
return ans;
}
vector<string> split(string& s, char delim) {
stringstream ss(s);
string item;
vector<string> res;
while (getline(ss, item, delim)) {
res.emplace_back(item);
}
return res;
}
};
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| func topStudents(positive_feedback []string, negative_feedback []string, report []string, student_id []int, k int) (ans []int) {
ps := map[string]bool{}
ns := map[string]bool{}
for _, s := range positive_feedback {
ps[s] = true
}
for _, s := range negative_feedback {
ns[s] = true
}
arr := [][2]int{}
for i, sid := range student_id {
t := 0
for _, w := range strings.Split(report[i], " ") {
if ps[w] {
t += 3
} else if ns[w] {
t -= 1
}
}
arr = append(arr, [2]int{t, sid})
}
sort.Slice(arr, func(i, j int) bool { return arr[i][0] > arr[j][0] || (arr[i][0] == arr[j][0] && arr[i][1] < arr[j][1]) })
for _, v := range arr[:k] {
ans = append(ans, v[1])
}
return
}
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| function topStudents(
positive_feedback: string[],
negative_feedback: string[],
report: string[],
student_id: number[],
k: number,
): number[] {
const n = student_id.length;
const map = new Map<number, number>();
const ps = new Set(positive_feedback);
const ns = new Set(negative_feedback);
for (let i = 0; i < n; i++) {
map.set(
student_id[i],
report[i].split(' ').reduce((r, s) => {
if (ps.has(s)) {
return r + 3;
}
if (ns.has(s)) {
return r - 1;
}
return r;
}, 0),
);
}
return [...map.entries()]
.sort((a, b) => {
if (a[1] === b[1]) {
return a[0] - b[0];
}
return b[1] - a[1];
})
.map(v => v[0])
.slice(0, k);
}
|
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| use std::collections::{ HashMap, HashSet };
impl Solution {
pub fn top_students(
positive_feedback: Vec<String>,
negative_feedback: Vec<String>,
report: Vec<String>,
student_id: Vec<i32>,
k: i32
) -> Vec<i32> {
let n = student_id.len();
let ps = positive_feedback.iter().collect::<HashSet<&String>>();
let ns = negative_feedback.iter().collect::<HashSet<&String>>();
let mut map = HashMap::new();
for i in 0..n {
let id = student_id[i];
let mut count = 0;
for s in report[i].split(' ') {
let s = &s.to_string();
if ps.contains(s) {
count += 3;
} else if ns.contains(s) {
count -= 1;
}
}
map.insert(id, count);
}
let mut t = map.into_iter().collect::<Vec<(i32, i32)>>();
t.sort_by(|a, b| {
if a.1 == b.1 {
return a.0.cmp(&b.0);
}
b.1.cmp(&a.1)
});
t.iter()
.map(|v| v.0)
.collect::<Vec<i32>>()
[0..k as usize].to_vec()
}
}
|
