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Java-based LeetCode algorithm problem solutions, regularly updated
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package g2501_2600.s2512_reward_top_k_students;

// #Medium #Array #String #Hash_Table #Sorting #Heap_Priority_Queue
// #2023_03_21_Time_72_ms_(94.76%)_Space_51.1_MB_(21.67%)

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.PriorityQueue;

/**
 * 2512 - Reward Top K Students\.
 *
 * Medium
 *
 * 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 <= 10⁴
 * *   `1 <= 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.length`
 * *   1 <= n <= 10⁴
 * *   `report[i]` consists of lowercase English letters and spaces `' '`.
 * *   There is a single space between consecutive words of `report[i]`.
 * *   `1 <= report[i].length <= 100`
 * *   1 <= student_id[i] <= 10⁹
 * *   All the values of `student_id[i]` are **unique**.
 * *   `1 <= k <= n`
**/
public class Solution {
    public List topStudents(
            String[] positiveFeedback,
            String[] negativeFeedback,
            String[] report,
            int[] studentId,
            int k) {
        HashMap feedback = new HashMap<>();
        for (String s : positiveFeedback) {
            feedback.put(s, 3);
        }
        for (String s : negativeFeedback) {
            feedback.put(s, -1);
        }
        PriorityQueue pq =
                new PriorityQueue<>(
                        (a, b) -> {
                            int result = Integer.compare(a.points, b.points);
                            return result == 0 ? Integer.compare(a.id, b.id) : -result;
                        });
        for (int i = 0; i < report.length; i++) {
            String[] split = report[i].split(" ");
            int sum = 0;
            for (String subStr : split) {
                sum += feedback.getOrDefault(subStr, 0);
            }
            pq.offer(new Student(studentId[i], sum));
        }
        List result = new ArrayList<>();
        while (!pq.isEmpty() && k-- > 0) {
            result.add(pq.poll().id);
        }
        return result;
    }

    private static class Student {
        int points;
        int id;

        public Student(int id, int points) {
            this.id = id;
            this.points = points;
        }
    }
}