2545. Sort the Students by Their Kth Score leetcode problem Solution c++ | How to sort 2D vectors in c++ using a custom comparator in c++

 2545. Sort the Students by Their Kth Score Solution c++-

How to sort 2D vectors in c++ using a custom comparator in c++.

This problem is part of leetcode 2545. Here we have to sort a 2D vector using custom comparator 

lets read problem statement first 

problem statement -

There is a class with m students and n exams. You are given a 0-indexed m x n integer matrix score, where each row represents one student and score[i][j] denotes the score the ith student got in the jth exam. The matrix score contains distinct integers only.

You are also given an integer k. Sort the students (i.e., the rows of the matrix) by their scores in the kth (0-indexed) exam from the highest to the lowest.

Return the matrix after sorting it.

 

Example 1:

Input: score = [[10,6,9,1],[7,5,11,2],[4,8,3,15]], k = 2
Output: [[7,5,11,2],[10,6,9,1],[4,8,3,15]]
Explanation: In the above diagram, S denotes the student, while E denotes the exam.
- The student with index 1 scored 11 in exam 2, which is the highest score, so they got first place.
- The student with index 0 scored 9 in exam 2, which is the second highest score, so they got second place.
- The student with index 2 scored 3 in exam 2, which is the lowest score, so they got third place.

Example 2:

Input: score = [[3,4],[5,6]], k = 0
Output: [[5,6],[3,4]]
Explanation: In the above diagram, S denotes the student, while E denotes the exam.
- The student with index 1 scored 5 in exam 0, which is the highest score, so they got first place.
- The student with index 0 scored 3 in exam 0, which is the lowest score, so they got second place.

 

Constraints:

• m == score.length
• n == score[i].length
• 1 <= m, n <= 250
• 1 <= score[i][j] <= 105
• score consists of distinct integers.
• 0 <= k < n

Explanation

Sort on A[i][k]

Complexity

Time O(quick sort)
Space O(quick sort)

Java

    public int[][] sortTheStudents(int[][] A, int k) {
        Arrays.sort(A, (a, b) -> b[k] - a[k]);
        return A;
    }

C++

    vector<vector<int>> sortTheStudents(vector<vector<int>>& A, int k) {
        sort(A.begin(), A.end(), [&](auto const & a, auto const & b) {
            return a[k] > b[k];
        });
        return A;
    }

C++

   static int i=0;

class Solution {

public:

   

   static bool compareScore(vector<int> &v1, vector<int> &v2){

    if(v1[i]>v2[i]){

        return true;

    }

    return false;

}

    vector<vector<int>> sortTheStudents(vector<vector<int>>& score, int k) {

       

        i=k;

        sort(score.begin(), score.end(), compareScore);

        return score;

       

    }  

};

Python
return new copy

    def sortTheStudents(self, A, k):
        return sorted(A, key=lambda a: -a[k])