LeetCode in Kotlin

1947. Maximum Compatibility Score Sum

Medium

There is a survey that consists of n questions where each question’s answer is either 0 (no) or 1 (yes).

The survey was given to m students numbered from 0 to m - 1 and m mentors numbered from 0 to m - 1. The answers of the students are represented by a 2D integer array students where students[i] is an integer array that contains the answers of the ith student (0-indexed). The answers of the mentors are represented by a 2D integer array mentors where mentors[j] is an integer array that contains the answers of the jth mentor (0-indexed).

Each student will be assigned to one mentor, and each mentor will have one student assigned to them. The compatibility score of a student-mentor pair is the number of answers that are the same for both the student and the mentor.

• For example, if the student’s answers were [1, 0, 1] and the mentor’s answers were [0, 0, 1], then their compatibility score is 2 because only the second and the third answers are the same.

You are tasked with finding the optimal student-mentor pairings to maximize the sum of the compatibility scores.

Given students and mentors, return the maximum compatibility score sum that can be achieved.

Example 1:

Input: students = [[1,1,0],[1,0,1],[0,0,1]], mentors = [[1,0,0],[0,0,1],[1,1,0]]

Output: 8

Explanation: We assign students to mentors in the following way:

• student 0 to mentor 2 with a compatibility score of 3.

• student 1 to mentor 0 with a compatibility score of 2.

student 2 to mentor 1 with a compatibility score of 3.

The compatibility score sum is 3 + 2 + 3 = 8.

Example 2:

Input: students = [[0,0],[0,0],[0,0]], mentors = [[1,1],[1,1],[1,1]]

Output: 0

Explanation: The compatibility score of any student-mentor pair is 0.

Constraints:

• m == students.length == mentors.length
• n == students[i].length == mentors[j].length
• 1 <= m, n <= 8
• students[i][k] is either 0 or 1.
• mentors[j][k] is either 0 or 1.

Solution

class Solution {
    private lateinit var dp: Array<IntArray>
    private var m = 0
    private lateinit var memo: Array<IntArray>

    fun maxCompatibilitySum(students: Array<IntArray>, mentors: Array<IntArray>): Int {
        val n = students[0].size
        m = students.size
        dp = Array(m) { IntArray(m) }
        for (i in 0 until m) {
            for (j in 0 until m) {
                var tmp = 0
                for (k in 0 until n) {
                    tmp += if (students[i][k] == mentors[j][k]) 1 else 0
                }
                dp[i][j] = tmp
            }
        }
        memo = Array(m) { IntArray((1 shl m) + 1) }
        for (x in memo) {
            x.fill(-1)
        }
        return dp(0, 0)
    }

    private fun dp(idx: Int, mask: Int): Int {
        if (idx == m) {
            return 0
        }
        if (memo[idx][mask] != -1) {
            return memo[idx][mask]
        }
        var ans = 0
        for (i in 0 until m) {
            if (mask and (1 shl i) == 0) {
                ans = Math.max(ans, dp[idx][i] + dp(idx + 1, mask or (1 shl i)))
            }
        }
        memo[idx][mask] = ans
        return ans
    }
}

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