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Java-based LeetCode algorithm problem solutions, regularly updated
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package g1601_1700.s1686_stone_game_vi;

// #Medium #Array #Math #Sorting #Greedy #Heap_Priority_Queue #Game_Theory
// #2022_04_18_Time_139_ms_(62.50%)_Space_60.1_MB_(73.53%)

import java.util.PriorityQueue;

/**
 * 1686 - Stone Game VI\.
 *
 * Medium
 *
 * Alice and Bob take turns playing a game, with Alice starting first.
 *
 * There are `n` stones in a pile. On each player's turn, they can **remove** a stone from the pile and receive points based on the stone's value. Alice and Bob may **value the stones differently**.
 *
 * You are given two integer arrays of length `n`, `aliceValues` and `bobValues`. Each `aliceValues[i]` and `bobValues[i]` represents how Alice and Bob, respectively, value the i^th stone.
 *
 * The winner is the person with the most points after all the stones are chosen. If both players have the same amount of points, the game results in a draw. Both players will play **optimally**. Both players know the other's values.
 *
 * Determine the result of the game, and:
 *
 * *   If Alice wins, return `1`.
 * *   If Bob wins, return `-1`.
 * *   If the game results in a draw, return `0`.
 *
 * **Example 1:**
 *
 * **Input:** aliceValues = [1,3], bobValues = [2,1]
 *
 * **Output:** 1
 *
 * **Explanation:** If Alice takes stone 1 (0-indexed) first, Alice will receive 3 points.
 *
 * Bob can only choose stone 0, and will only receive 2 points.
 *
 * Alice wins.
 *
 * **Example 2:**
 *
 * **Input:** aliceValues = [1,2], bobValues = [3,1]
 *
 * **Output:** 0
 *
 * **Explanation:** If Alice takes stone 0, and Bob takes stone 1, they will both have 1 point.
 *
 * Draw.
 *
 * **Example 3:**
 *
 * **Input:** aliceValues = [2,4,3], bobValues = [1,6,7]
 *
 * **Output:** -1
 *
 * **Explanation:** Regardless of how Alice plays, Bob will be able to have more points than Alice.
 *
 * For example, if Alice takes stone 1, Bob can take stone 2, and Alice takes stone 0, Alice will have 6 points to Bob's 7.
 *
 * Bob wins.
 *
 * **Constraints:**
 *
 * *   `n == aliceValues.length == bobValues.length`
 * *   1 <= n <= 10⁵
 * *   `1 <= aliceValues[i], bobValues[i] <= 100`
**/
@SuppressWarnings("java:S1210")
public class Solution {
    private static class Pair implements Comparable {
        int sum;
        int a;
        int b;

        Pair(int a, int b) {
            this.sum = a + b;
            this.a = a;
            this.b = b;
        }

        public int compareTo(Pair p) {
            return p.sum - this.sum;
        }
    }

    public int stoneGameVI(int[] aliceValues, int[] bobValues) {
        PriorityQueue pq = new PriorityQueue<>();
        for (int i = 0; i < aliceValues.length; i++) {
            pq.add(new Pair(aliceValues[i], bobValues[i]));
        }
        boolean turn = true;
        int a = 0;
        int b = 0;
        while (!pq.isEmpty()) {
            if (turn) {
                a += pq.poll().a;
            } else {
                b += pq.poll().b;
            }
            turn = !turn;
        }
        return Integer.compare(a, b);
    }
}